There's a Mexican guy called "Alucardio" in YouTube and he makes a tutorial about indexiine but with different steps and files. I Would highly recommed to download his files and follow his steps you'll have no problems with his tutorial in YouTube "HACK CFW OFFLINE WII U SIN JUEGOS NDS + DESDE...
After facing multiples issues, i managed to make it work. My wii u is currently on 5.5.3 and i was having an issue. Indexiine wasn't working when launching in the browser i waited more than 10 seconds and nothing happened. i reset my wii u several times and try to make this hack work but stills...
@Xdqwerty, Osu! Tatakae! Ouendan! is the Japanese version of the game, different settings/characters/songs but otherwise identical mechanics. I played that before I knew about Elite Beat Agents lol. Both fantastic games https://en.wikipedia.org/wiki/Osu!_Tatakae!_Ouendan