Inko and Mitsuki where friends and decided to host Christmas together this year at Inko's house meaning they where going to stay over on Christmas eve. She obviously brought bakugo who was only four years old at the time and deku was already there it being his house and all playing with some toys in the living room also is four they where good friends and bakugo never ends up bullying deku.

when they arrive before Mitsuki knocks on the door she gives bakugo a thorough warning about his behaviour and warning him not tk act like a brat Infront of people and to treat deku right.

when she knocked on the door she was greeted by a cheerful Inko who was wearing a Christmas jumper and they gave eachother a hug.

Bakugo stands there looking bored untill he sees deku in the living room and smiles he went running in towards deku

"Dekuuuu!!!"