I got this basically right after the HRHD SS. I was just like, "eh, why not get them both?"
I believe I actually had an SS on this song at one point, but I didn't let it go through because I wasn't ready to submit 4* songs at the time. I still count Jaakuningatar as the first, personally, though.
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 4,503 views in 935 videos for osu!. His channel published over 1 day worth of content for the game, roughly 21.26% of osu! content that JonathanScarlet has uploaded to YouTube.