You were being silly and found something at the store that you thought Aizawa would like so you forced him to wear it. That's it.

You had found matching cat hoodies and immediately booked it back to UA after buying them and forced Shota to wear one.

One was a black cat (obviously the one Aizawa was wearing) and then a brown-spotted Savannah cat hoodie. He loved it. He absolutely adored the hoodies.

Shota stood with his arms crossed, in the cat hoodie, and groaned in feigned annoyance.

"Hm...."