Follow Your Passion: A Seamless Tumblr Journey
So I remember some of the fanfic. And it's during the summertime when Adrien takes shelter in this abandoned building with stuff all set up, I remember there was a bed and near this building, he finds a party one night and dances there. But Gabriel is looking for him but can only figure it out from chat noir who has clues for him to figure out something important for Adrien to come home. Then Plagg teaches Adrien magic, how ladybug found out he's been living there and she also trains with magic. Do they go through this old/ancient building that has this old curse?
Trying to figure out the origins. I also remember Adrien getting a toy piano and playing a song from that cat Disney movie before Gabriel interrupted it. And some how this ends up with Adrien coming home and revealing his identity. It's either on ao3 or fanfic.net, though I'm pretty sure it's fanfic.net. Title has something with sun or related to it.