The new Oh God Yes! event is basically Guitar Hero, which is actually a little bit fun. Same formula as the last few events, you do the minigame in stages, and you unlock a sex scene when you unlock 8 girls. It's apparently an orgy, I guess like the Easter one, so I assume it gets bigger with more girls unlocked, but why it is locked behind the 8 girls requirement, I don't know. I'm assuming the pairings in it will conform to tier status, like Cherry with Lola, Sanshi with Ice etc, which is a mistake they learned from the Easter orgy.

It does take a little while to unlock each girl, so you might be better off just doing 1-2 girls a day, just so you don't get bored of the minigame.