I believe Marisa was going for a secret kiss while Rinnosuke was asleep, but he woke up just before she did the deed. She got startled, panicked, and lashed out.
This cliche' is also pretty damn in as an Anime Trope. More often than note, the recipient will ALWAYS wake up while the girl is about to make the kiss.
Rinnosuke got off easy. If Marisa was a stereotype Tsundere, he would have gotten more of a beating.
