My perverted girlfriend

Hina and Yonezu are a couple. Everything seems fine until one day Yonezu happens to witness Hina satisfying herself in a remote park. Yonezu cannot believe his eyes. After all he knew her to be a very different person, namely a cute girl who went to an elite college. So what’s to b e done? At last Yonezu decides to question Hina. But what he is about to find out is more than he had ever imagined...