Back in 2012 i used to watch Starcraft 2 streamers a lot. I was watching a player called KawaiiRice play SC2 and he was doing his warm-up before the stream. He open a game that i originally thought was some sort of music player from the huge selection of songs. Then i saw him start playing the songs to the beat. I was curious what it was and posted in his chat, "Wtf game is this".
People in chat said Osu! and i went on my way to get it. I thought it was going to come with that huge song list that KawaiiRice had, but it didn't and i realized i had to individually download songs. I got a beatmap pack and was on my way. I eventually youtubed the game and i saw cookiezi big black play and was blown away. I wanted to do that also because it looked so impressive, so i began playing a lot. Even when i stopped watching KawaiiRice, i still played Osu! I wasn't like a huge fan of his, i was just browsing popular SC2 streams, but i am so happy i came in when i did.