download whole series from Yugenanime / yugenani.me.
open the dev console on the first episode by pressing:
ctrl + shift + j or rightclick -> ispect element -> second tab, says "console".
all instructions there.
this script produces links you can then paste into a download manager.
supports first 3 yugenani.me servers.
THIS SCRIPT REQUIRES your userscript manager to have the GM_ API built in. Either use a old version of Grease monkey that still supports them, any version of violentmonkey either beta or normal. i don't know about tampermonkey, it maybe works.
if you would like a quicker, more reliable solution written in python that works on gogoanime(they use the same anime provider as yugen), check out https://github.com/KraXen72/gogoanime-downloader