He's just happy they're no longer fraught, pushing each other away despite having known each other long enough to catch each other's idiosyncrasies when others don't. By all rights, they should have drifted apart and completely ignored each other in childhood. It would have been the healthy thing. Midoriya's kindness shouldn't have offended (frightened) Bakugou. Bakugou's strength shouldn't have inspired admiration in Midoriya.

Seeking what they each lacked, and finding it by observing its potency each other, made them converge. Admiring the same methods and principles in All Might, and excelling at them right under each other's noses, ensured they would orbit around each other like twin stars--whether they liked it or not.

They figured out how to do it properly. Things were touch and go, but it was good. They made each other better. Then Midoriya was taken away from him and everyone else, save just one friend, and he lost so much. Damn right he's used to copying the memory of his missing friends. He's been doing it for months, trying to fill the holes in his heart and soothe the scars on his body.

He bats the shower curtain aside so it won't get pulled. Bakugou taught him (by example, he didn't actually teach him) to fight even when someone grabs his face. As he inevitably pitches back into the tub, he does what he's been doing since last summer when he asked Iida to show him some moves: He fights with his legs.

He hooks his legs around Bakugou's and jerks with his whole body. If he's going down, he's taking Bakugou with him.