I forgot to do day 11 yesterday, so I'll do both Day 11 and Day 12 today

Day 11 - Favorite original song by Poppin' Party

A tie betweenInitial and Breakthrough

Day 12 - Favorite original song by Afterglow

My favorite one so far is I knew it. I hope they release their full version soon.

Credits to Riru for making this challenge board.