Once he stops panicking about being here, Atsumu is a cheeky little shit, so I'm sure Howl will adore him (or tolerate him) Also look he's already met Amos, and will be meeting Emet, fellow brainwashed buddy Barnaby, and world's most sketchy dad Silco. Howl will fit riiiiight in with the adults soon to be in Atsumu's life