I was too focused on playing, so I kinda want to know what the hell is going on. Not that I'm interested enough to watch the MV itself since I'm not that big a fan of the song. Guess I'll just have to stay curious.
Osu! is a rhythm game based off of Osu! Tatakae! Ouendan! and the American release Elite Beat Agents. In these games you click circles to the rhythm of the song. Osu! also has different rankings you can shoot for, with SS being the best (Hit every note and have 100% accuracy). There are also mods like Hard Rock, Hidden, Flashlight, and Double Time/Nightcore if you want to increase the difficulty even more.
There are 3,996 views in 788 videos for osu!. His channel published over 1 day worth of content for the game, roughly 20.07% of osu! content that JonathanScarlet has uploaded to YouTube.