How to convert the httprequest result to EUC-JP by GM_xmlhttpRequest with encoding.min.js API?

I get the httprequest result from a URL whose charset is EUC-JP and shows Garbled characters.

I tried to get the Buffer result and convert it to EUC-JP, but the result still shows garbled characters.

How to get the UTF8 result?

// ==UserScript==
// @name         New Userscript
// @namespace    http://tampermonkey.net/
// @version      2024-08-25
// @description  try to take over the world!
// @author       You
// @match        http://*/*
// @icon         data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==
// @grant        none
// @require      https://cdn.jsdelivr.net/npm/[email protected]/dist/jquery.min.js
// @require      https://cdn.jsdelivr.net/npm/[email protected]/encoding.min.js

// ==/UserScript==
    function convertBufferToEucJp(buffer) {
        // Convert buffer to Uint8Array
        const uint8Array = new Uint8Array(buffer);

        // Convert Uint8Array to string with UTF-8 encoding (assuming the buffer is UTF-8)
        const utf8String = new TextDecoder("utf-8").decode(uint8Array);

        // Convert UTF-8 string to EUC-JP
        const eucJpString = Encoding.convert(utf8String, {
            to: 'EUCJP',
            from: 'UTF8'
        });

        return eucJpString;
    }

    GM_xmlhttpRequest({
        method: "GET",
        url: "https://seesaawiki.jp/av_video/d/%c6%e1%b2%ec%ba%ea%a4%e6%a4%ad%a4%cd",
        responseType: "arraybuffer", // Get response as ArrayBuffer
        onload: function(response) {
            if (response.status >= 200 && response.status < 300) {
                // Convert ArrayBuffer to EUC-JP string
                const eucJpString = convertBufferToEucJp(response.response);

                // Do something with the EUC-JP string
                console.log(eucJpString);
            } else {
                console.error("Error fetching data:", response.status);
            }
        },
        onerror: function(error) {
            console.error("Request error:", error);
        },
    });