diff --git a/src/context.ts b/src/context.ts
index b8f0e4b4..86124e00 100644
--- a/src/context.ts
+++ b/src/context.ts
@@ -623,11 +623,11 @@ export class Context<
     return Object.fromEntries(this.#var)
   }
 
-  newResponse: NewResponse = (
+  #newResponse(
     data: Data | null,
     arg?: StatusCode | ResponseInit,
     headers?: HeaderRecord
-  ): Response => {
+  ): Response {
     // Optimized
     if (this.#isFresh && !headers && !arg && this.#status === 200) {
       return new Response(data, {
@@ -689,6 +689,8 @@ export class Context<
     })
   }
 
+  newResponse: NewResponse = (...args) => this.#newResponse(...(args as Parameters<NewResponse>))
+
   /**
    * `.body()` can return the HTTP response.
    * You can set headers with `.header()` and set HTTP status code with `.status`.
@@ -716,8 +718,8 @@ export class Context<
     headers?: HeaderRecord
   ): Response => {
     return typeof arg === 'number'
-      ? this.newResponse(data, arg, headers)
-      : this.newResponse(data, arg)
+      ? this.#newResponse(data, arg, headers)
+      : this.#newResponse(data, arg)
   }
 
   /**
@@ -749,8 +751,8 @@ export class Context<
     this.#preparedHeaders['content-type'] = TEXT_PLAIN
     // @ts-expect-error `Response` due to missing some types-only keys
     return typeof arg === 'number'
-      ? this.newResponse(text, arg, headers)
-      : this.newResponse(text, arg)
+      ? this.#newResponse(text, arg, headers)
+      : this.#newResponse(text, arg)
   }
 
   /**
@@ -778,7 +780,7 @@ export class Context<
     this.#preparedHeaders['content-type'] = 'application/json; charset=UTF-8'
     /* eslint-disable @typescript-eslint/no-explicit-any */
     return (
-      typeof arg === 'number' ? this.newResponse(body, arg, headers) : this.newResponse(body, arg)
+      typeof arg === 'number' ? this.#newResponse(body, arg, headers) : this.#newResponse(body, arg)
     ) as any
   }
 
@@ -793,14 +795,14 @@ export class Context<
     if (typeof html === 'object') {
       return resolveCallback(html, HtmlEscapedCallbackPhase.Stringify, false, {}).then((html) => {
         return typeof arg === 'number'
-          ? this.newResponse(html, arg, headers)
-          : this.newResponse(html, arg)
+          ? this.#newResponse(html, arg, headers)
+          : this.#newResponse(html, arg)
       })
     }
 
     return typeof arg === 'number'
-      ? this.newResponse(html as string, arg, headers)
-      : this.newResponse(html as string, arg)
+      ? this.#newResponse(html as string, arg, headers)
+      : this.#newResponse(html as string, arg)
   }
 
   /**
diff --git a/src/hono-base.ts b/src/hono-base.ts
index ea23ec26..88a5ec7c 100644
--- a/src/hono-base.ts
+++ b/src/hono-base.ts
@@ -130,11 +130,11 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
         if (typeof args1 === 'string') {
           this.#path = args1
         } else {
-          this.addRoute(method, this.#path, args1)
+          this.#addRoute(method, this.#path, args1)
         }
         args.forEach((handler) => {
           if (typeof handler !== 'string') {
-            this.addRoute(method, this.#path, handler)
+            this.#addRoute(method, this.#path, handler)
           }
         })
         return this as any
@@ -147,7 +147,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
         this.#path = p
         for (const m of [method].flat()) {
           handlers.map((handler) => {
-            this.addRoute(m.toUpperCase(), this.#path, handler)
+            this.#addRoute(m.toUpperCase(), this.#path, handler)
           })
         }
       }
@@ -163,7 +163,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
         handlers.unshift(arg1)
       }
       handlers.forEach((handler) => {
-        this.addRoute(METHOD_NAME_ALL, this.#path, handler)
+        this.#addRoute(METHOD_NAME_ALL, this.#path, handler)
       })
       return this as any
     }
@@ -174,7 +174,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
     this.getPath = strict ? options.getPath ?? getPath : getPathNoStrict
   }
 
-  private clone(): Hono<E, S, BasePath> {
+  #clone(): Hono<E, S, BasePath> {
     const clone = new Hono<E, S, BasePath>({
       router: this.router,
       getPath: this.getPath,
@@ -183,8 +183,8 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
     return clone
   }
 
-  private notFoundHandler: NotFoundHandler = notFoundHandler
-  private errorHandler: ErrorHandler = errorHandler
+  #notFoundHandler: NotFoundHandler = notFoundHandler
+  #errorHandler: ErrorHandler = errorHandler
 
   /**
    * `.route()` allows grouping other Hono instance in routes.
@@ -216,15 +216,15 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
     const subApp = this.basePath(path)
     app.routes.map((r) => {
       let handler
-      if (app.errorHandler === errorHandler) {
+      if (app.#errorHandler === errorHandler) {
         handler = r.handler
       } else {
         handler = async (c: Context, next: Next) =>
-          (await compose<Context>([], app.errorHandler)(c, () => r.handler(c, next))).res
+          (await compose<Context>([], app.#errorHandler)(c, () => r.handler(c, next))).res
         ;(handler as any)[COMPOSED_HANDLER] = r.handler
       }
 
-      subApp.addRoute(r.method, r.path, handler)
+      subApp.#addRoute(r.method, r.path, handler)
     })
     return this
   }
@@ -243,7 +243,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
    * ```
    */
   basePath<SubPath extends string>(path: SubPath): Hono<E, S, MergePath<BasePath, SubPath>> {
-    const subApp = this.clone()
+    const subApp = this.#clone()
     subApp._basePath = mergePath(this._basePath, path)
     return subApp
   }
@@ -265,7 +265,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
    * ```
    */
   onError = (handler: ErrorHandler<E>): Hono<E, S, BasePath> => {
-    this.errorHandler = handler
+    this.#errorHandler = handler
     return this
   }
 
@@ -285,7 +285,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
    * ```
    */
   notFound = (handler: NotFoundHandler<E>): Hono<E, S, BasePath> => {
-    this.notFoundHandler = handler
+    this.#notFoundHandler = handler
     return this
   }
 
@@ -370,11 +370,11 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
 
       await next()
     }
-    this.addRoute(METHOD_NAME_ALL, mergePath(path, '*'), handler)
+    this.#addRoute(METHOD_NAME_ALL, mergePath(path, '*'), handler)
     return this
   }
 
-  private addRoute(method: string, path: string, handler: H) {
+  #addRoute(method: string, path: string, handler: H) {
     method = method.toUpperCase()
     path = mergePath(this._basePath, path)
     const r: RouterRoute = { path: path, method: method, handler: handler }
@@ -382,14 +382,14 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
     this.routes.push(r)
   }
 
-  private handleError(err: unknown, c: Context<E>) {
+  #handleError(err: unknown, c: Context<E>) {
     if (err instanceof Error) {
-      return this.errorHandler(err, c)
+      return this.#errorHandler(err, c)
     }
     throw err
   }
 
-  private dispatch(
+  #dispatch(
     request: Request,
     executionCtx: ExecutionContext | FetchEventLike | undefined,
     env: E['Bindings'],
@@ -398,7 +398,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
     // Handle HEAD method
     if (method === 'HEAD') {
       return (async () =>
-        new Response(null, await this.dispatch(request, executionCtx, env, 'GET')))()
+        new Response(null, await this.#dispatch(request, executionCtx, env, 'GET')))()
     }
 
     const path = this.getPath(request, { env })
@@ -409,7 +409,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
       matchResult,
       env,
       executionCtx,
-      notFoundHandler: this.notFoundHandler,
+      notFoundHandler: this.#notFoundHandler,
     })
 
     // Do not `compose` if it has only one handler
@@ -417,23 +417,23 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
       let res: ReturnType<H>
       try {
         res = matchResult[0][0][0][0](c, async () => {
-          c.res = await this.notFoundHandler(c)
+          c.res = await this.#notFoundHandler(c)
         })
       } catch (err) {
-        return this.handleError(err, c)
+        return this.#handleError(err, c)
       }
 
       return res instanceof Promise
         ? res
             .then(
               (resolved: Response | undefined) =>
-                resolved || (c.finalized ? c.res : this.notFoundHandler(c))
+                resolved || (c.finalized ? c.res : this.#notFoundHandler(c))
             )
-            .catch((err: Error) => this.handleError(err, c))
-        : res ?? this.notFoundHandler(c)
+            .catch((err: Error) => this.#handleError(err, c))
+        : res ?? this.#notFoundHandler(c)
     }
 
-    const composed = compose<Context>(matchResult[0], this.errorHandler, this.notFoundHandler)
+    const composed = compose<Context>(matchResult[0], this.#errorHandler, this.#notFoundHandler)
 
     return (async () => {
       try {
@@ -446,7 +446,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
 
         return context.res
       } catch (err) {
-        return this.handleError(err, c)
+        return this.#handleError(err, c)
       }
     })()
   }
@@ -467,7 +467,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
     Env?: E['Bindings'] | {},
     executionCtx?: ExecutionContext
   ) => Response | Promise<Response> = (request, ...rest) => {
-    return this.dispatch(request, rest[1], rest[0], request.method)
+    return this.#dispatch(request, rest[1], rest[0], request.method)
   }
 
   /**
@@ -511,7 +511,7 @@ class Hono<E extends Env = Env, S extends Schema = {}, BasePath extends string =
     // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-ignore
     addEventListener('fetch', (event: FetchEventLike): void => {
-      event.respondWith(this.dispatch(event.request, event, undefined, event.request.method))
+      event.respondWith(this.#dispatch(event.request, event, undefined, event.request.method))
     })
   }
 }
diff --git a/src/request.ts b/src/request.ts
index a3f68f9d..68c710c3 100644
--- a/src/request.ts
+++ b/src/request.ts
@@ -91,21 +91,21 @@ export class HonoRequest<P extends string = '/', I extends Input['out'] = {}> {
   param(key: string): string | undefined
   param<P2 extends string = P>(): Simplify<UnionToIntersection<ParamKeyToRecord<ParamKeys<P2>>>>
   param(key?: string): unknown {
-    return key ? this.getDecodedParam(key) : this.getAllDecodedParams()
+    return key ? this.#getDecodedParam(key) : this.#getAllDecodedParams()
   }
 
-  private getDecodedParam(key: string): string | undefined {
+  #getDecodedParam(key: string): string | undefined {
     const paramKey = this.#matchResult[0][this.routeIndex][1][key]
-    const param = this.getParamValue(paramKey)
+    const param = this.#getParamValue(paramKey)
     return param ? (/\%/.test(param) ? tryDecodeURIComponent(param) : param) : undefined
   }
 
-  private getAllDecodedParams(): Record<string, string> {
+  #getAllDecodedParams(): Record<string, string> {
     const decoded: Record<string, string> = {}
 
     const keys = Object.keys(this.#matchResult[0][this.routeIndex][1])
     for (const key of keys) {
-      const value = this.getParamValue(this.#matchResult[0][this.routeIndex][1][key])
+      const value = this.#getParamValue(this.#matchResult[0][this.routeIndex][1][key])
       if (value && typeof value === 'string') {
         decoded[key] = /\%/.test(value) ? tryDecodeURIComponent(value) : value
       }
@@ -114,7 +114,7 @@ export class HonoRequest<P extends string = '/', I extends Input['out'] = {}> {
     return decoded
   }
 
-  private getParamValue(paramKey: any): string | undefined {
+  #getParamValue(paramKey: any): string | undefined {
     return this.#matchResult[1] ? this.#matchResult[1][paramKey as any] : paramKey
   }
 
@@ -208,7 +208,7 @@ export class HonoRequest<P extends string = '/', I extends Input['out'] = {}> {
     return (this.bodyCache.parsedBody ??= await parseBody(this, options))
   }
 
-  private cachedBody = (key: keyof Body) => {
+  #cachedBody = (key: keyof Body) => {
     const { bodyCache, raw } = this
     const cachedBody = bodyCache[key]
 
@@ -242,7 +242,7 @@ export class HonoRequest<P extends string = '/', I extends Input['out'] = {}> {
    * ```
    */
   json<T = any>(): Promise<T> {
-    return this.cachedBody('json')
+    return this.#cachedBody('json')
   }
 
   /**
@@ -258,7 +258,7 @@ export class HonoRequest<P extends string = '/', I extends Input['out'] = {}> {
    * ```
    */
   text(): Promise<string> {
-    return this.cachedBody('text')
+    return this.#cachedBody('text')
   }
 
   /**
@@ -274,7 +274,7 @@ export class HonoRequest<P extends string = '/', I extends Input['out'] = {}> {
    * ```
    */
   arrayBuffer(): Promise<ArrayBuffer> {
-    return this.cachedBody('arrayBuffer')
+    return this.#cachedBody('arrayBuffer')
   }
 
   /**
@@ -288,7 +288,7 @@ export class HonoRequest<P extends string = '/', I extends Input['out'] = {}> {
    * @see https://hono.dev/docs/api/request#blob
    */
   blob(): Promise<Blob> {
-    return this.cachedBody('blob')
+    return this.#cachedBody('blob')
   }
 
   /**
@@ -302,7 +302,7 @@ export class HonoRequest<P extends string = '/', I extends Input['out'] = {}> {
    * @see https://hono.dev/docs/api/request#formdata
    */
   formData(): Promise<FormData> {
-    return this.cachedBody('formData')
+    return this.#cachedBody('formData')
   }
 
   /**
diff --git a/src/router/pattern-router/router.ts b/src/router/pattern-router/router.ts
index db90bee7..fb819b21 100644
--- a/src/router/pattern-router/router.ts
+++ b/src/router/pattern-router/router.ts
@@ -5,7 +5,7 @@ type Route<T> = [RegExp, string, T] // [pattern, method, handler, path]
 
 export class PatternRouter<T> implements Router<T> {
   name: string = 'PatternRouter'
-  private routes: Route<T>[] = []
+  #routes: Route<T>[] = []
 
   add(method: string, path: string, handler: T) {
     const endsWithWildcard = path[path.length - 1] === '*'
@@ -34,14 +34,14 @@ export class PatternRouter<T> implements Router<T> {
     } catch {
       throw new UnsupportedPathError()
     }
-    this.routes.push([re, method, handler])
+    this.#routes.push([re, method, handler])
   }
 
   match(method: string, path: string): Result<T> {
     const handlers: [T, Params][] = []
 
-    for (let i = 0, len = this.routes.length; i < len; i++) {
-      const [pattern, routeMethod, handler] = this.routes[i]
+    for (let i = 0, len = this.#routes.length; i < len; i++) {
+      const [pattern, routeMethod, handler] = this.#routes[i]
 
       if (routeMethod === method || routeMethod === METHOD_NAME_ALL) {
         const match = pattern.exec(path)
diff --git a/src/router/reg-exp-router/router.ts b/src/router/reg-exp-router/router.ts
index 95f840e7..c3358885 100644
--- a/src/router/reg-exp-router/router.ts
+++ b/src/router/reg-exp-router/router.ts
@@ -207,7 +207,7 @@ export class RegExpRouter<T> implements Router<T> {
   match(method: string, path: string): Result<T> {
     clearWildcardRegExpCache() // no longer used.
 
-    const matchers = this.buildAllMatchers()
+    const matchers = this.#buildAllMatchers()
 
     this.match = (method, path) => {
       const matcher = (matchers[method] || matchers[METHOD_NAME_ALL]) as Matcher<T>
@@ -229,13 +229,13 @@ export class RegExpRouter<T> implements Router<T> {
     return this.match(method, path)
   }
 
-  private buildAllMatchers(): Record<string, Matcher<T> | null> {
+  #buildAllMatchers(): Record<string, Matcher<T> | null> {
     const matchers: Record<string, Matcher<T> | null> = Object.create(null)
 
     Object.keys(this.routes!)
       .concat(Object.keys(this.middleware!))
       .forEach((method) => {
-        matchers[method] ||= this.buildMatcher(method)
+        matchers[method] ||= this.#buildMatcher(method)
       })
 
     // Release cache
@@ -244,7 +244,7 @@ export class RegExpRouter<T> implements Router<T> {
     return matchers
   }
 
-  private buildMatcher(method: string): Matcher<T> | null {
+  #buildMatcher(method: string): Matcher<T> | null {
     const routes: [string, HandlerWithMetadata<T>[]][] = []
 
     let hasOwnRoute = method === METHOD_NAME_ALL
diff --git a/src/router/trie-router/node.ts b/src/router/trie-router/node.ts
index 61e6ba45..3130433b 100644
--- a/src/router/trie-router/node.ts
+++ b/src/router/trie-router/node.ts
@@ -82,7 +82,7 @@ export class Node<T> {
   }
 
   // getHandlerSets
-  private gHSets(
+  #gHSets(
     node: Node<T>,
     method: string,
     nodeParams: Record<string, string>,
@@ -133,10 +133,10 @@ export class Node<T> {
             // '/hello/*' => match '/hello'
             if (nextNode.children['*']) {
               handlerSets.push(
-                ...this.gHSets(nextNode.children['*'], method, node.params, Object.create(null))
+                ...this.#gHSets(nextNode.children['*'], method, node.params, Object.create(null))
               )
             }
-            handlerSets.push(...this.gHSets(nextNode, method, node.params, Object.create(null)))
+            handlerSets.push(...this.#gHSets(nextNode, method, node.params, Object.create(null)))
           } else {
             tempNodes.push(nextNode)
           }
@@ -152,7 +152,7 @@ export class Node<T> {
           if (pattern === '*') {
             const astNode = node.children['*']
             if (astNode) {
-              handlerSets.push(...this.gHSets(astNode, method, node.params, Object.create(null)))
+              handlerSets.push(...this.#gHSets(astNode, method, node.params, Object.create(null)))
               tempNodes.push(astNode)
             }
             continue
@@ -170,7 +170,7 @@ export class Node<T> {
           const restPathString = parts.slice(i).join('/')
           if (matcher instanceof RegExp && matcher.test(restPathString)) {
             params[name] = restPathString
-            handlerSets.push(...this.gHSets(child, method, node.params, params))
+            handlerSets.push(...this.#gHSets(child, method, node.params, params))
             continue
           }
 
@@ -178,9 +178,11 @@ export class Node<T> {
             if (typeof key === 'string') {
               params[name] = part
               if (isLast) {
-                handlerSets.push(...this.gHSets(child, method, params, node.params))
+                handlerSets.push(...this.#gHSets(child, method, params, node.params))
                 if (child.children['*']) {
-                  handlerSets.push(...this.gHSets(child.children['*'], method, params, node.params))
+                  handlerSets.push(
+                    ...this.#gHSets(child.children['*'], method, params, node.params)
+                  )
                 }
               } else {
                 child.params = params