Does not being able to read manga on KissManga.com just by using your keyboard bother you? Well this quick script will fix that by enabling to change chapters by using keyboard left and right arrow keys while enabling support for W/S scrolling for the left handed people.

kissMangaEnhancements.user.js

// ==UserScript==
// @name         KissManga Quick Enhancements
// @author       Manciuszz
// @version      0.1
// @match        *://kissmanga.com/Manga/*/*
// ==/UserScript==

(function() {
    'use strict';

    let scrollTo = function(to, duration) { // Credits to https://gist.github.com/andjosh/6764939 for this one.
        let element = document.scrollingElement || document.documentElement,
            start = element.scrollTop,
            change = to - start,
            startDate = +new Date(),
            easeInOutQuad = function(t, b, c, d) {
                t /= d/2;
                if (t < 1) return c/2*t*t + b;
                t--;
                return -c/2 * (t*(t-2) - 1) + b;
            },
            animateScroll = function() {
                const currentDate = +new Date();
                const currentTime = currentDate - startDate;
                element.scrollTop = parseInt(easeInOutQuad(currentTime, start, change, duration));
                if (currentTime < duration) {
                    requestAnimationFrame(animateScroll);
                } else {
                    element.scrollTop = to;
                }
            };
        animateScroll();
    };

    let scrollIncrementor = function(direction = 1, step = 100) {
        return window.scrollY + step * direction;
    };

    $(document).on('keydown', function(evt) {
        if (evt.keyCode === 37) { // LEFT
            window.location.href = $("img.btnPrevious").parent('a').get(0).href;
        } else if (evt.keyCode === 39) { // RIGHT
            window.location.href = $("img.btnNext").parent('a').get(0).href;
        } else if (evt.keyCode === 87) { // W
            scrollTo(scrollIncrementor(-1, 200), 100);
        } else if (evt.keyCode === 83) { // S
            scrollTo(scrollIncrementor(1, 200), 100);
        }
    });
})();