There's the "punching" tag in the tag list, so it Kuma who punched Kitakami and the latter's head hit the desk afterwards.
That's the joke. Kuma can't hit Kitakami by herself. She had to use something else like a wall or piece of furniture to do damage.
That's right!This suuucks!Alright!Ohh... you're all such serious kiddos...No way kuma!You gotta choose, carefully and seriously kuma!Working in the shipgirl employment examination, Kitakami.We came here because we seriously wanted to protect the peace!Right then, everyone passes!