ツインズ・パニック ～おにいちゃんは私たちの奴隷～

The male protagonist, an university student named Kouji, has moved into an apartment whose landlady has two beautiful twin daughters, Yuumi and Yuuka, and of course both twins take an instant fancy to him (although not exactly with his best interests in mind, heh).
You can imagine the rest, can't you?