The green haired one is his sister, he hooks up with the red head.
The whole show is basically fanservice, characters setting themselves up in awkward sexual positions like when the girls are dashing towards the...uh, dude guy person, to give him a hug, both of them trip at the same time, and land in >>12917189
That's basically the entire show after the first episode or two.
To be honest I liked the startup more than anything else because the protagonist seemed a lot more mature and in charge of things, but as it dragged on he sort of did a Squall-like personality flip that just came out of nowhere. One minute he's all "godjesus I can't wait till you get out of my house" and the next he's like "I'LL NEVER LEAVE YOU EVER EVER"