Name of a manga I read a long time ago?

It's an ecchi, harem, manga that might have been a little adult, it was about a boy who's girlfriend had two sisters who were protective and perverted. They had with him to drive him away from their sister, and eventually they fall in love with him too. At one point the capture this girl who is mean to him, or something, and they her up to....with vibrators and stuff.....