The fuse on the (proverbial) bomb burns closer and closer ... and only Kami-Sama (and Hirno-sensei) knows what will happen when it burns all the way out.
Ooh, a sequel? Nice. Kind of makes me want another sequel, make this a series or something. Also I still kinda want to see her sister get some loving too.
"I wonder if I might be better off breaking up with Haruka-san"? The fact that he even considered this is worthy of at least a bit of praise, I think. Most don't even consider that course of action. Unfortunately, he didn't quite go through with it and it was just a thought, but I suppose that's kind of expected.
Considering how good natured her sister is, I almost think she'd accept sharing him, but I doubt it'll happen as long as they don't get careless with the pictures or give themselves away.
After the last page I'm waiting for Slow Rhythm 3 where the girlfriend DOES find out and all hell break lose. Or we could have a totally surprisingly sequel in which the girlfriend actually likes NTR and is with the sister.