You guys live in one apartment, you guys travel together, fight together but he's still egoistic, one day Albedo visited Sumeru and wanted to test a potion on you but you weren't there so... he tested something on Wanderer, after a few hours Albedo texted you

"Please come here I may have made a mistake"

When you returned to your apartment Albedo is already gone and Wanderer is hiding under a blanket with a... Tail and ears like a cat?!

"Look what your alchemist friend did to me!?"