userscripts/download/y-media-downloader.js

// ==UserScript==
// @name        y-media-downloader
// @description General media downloader
// @author      17ms
// @license     MIT License
// @namespace   Violentmonkey Scripts
// @match       *://ylilauta.org/*
// @version     1.0
// ==/UserScript==

function download(url) {
    fetch(url, {
        mode: "no-cors",
    })
        .then((response) => response.blob())
        .then((blob) => {
            let blob_url = window.URL.createObjectURL(blob)
            let a = document.createElement("a")
            a.download = url.split("/")[5]
            a.href = blob_url
            document.body.appendChild(a)
            a.click()
            a.remove()
        })
}

function init() {
    const links = Array.from(document.getElementsByClassName("jpg")).concat(
        Array.from(document.getElementsByClassName("png"))
    )

    for (let i = 0; i < links.length; ++i) {
        let url = links[i].href
        download(url)
    }
}

const activate_link = document.createElement("button")
const parent_element = document.getElementById("navbar")
activate_link.innerText = "⮶"
activate_link.style.fontSize = "30px"
activate_link.onclick = () => init()
parent_element.append(activate_link)