I hope there is no need to mark anything about the OVA as spoilers, since the title already says so.
Anyway, I really don't like what the OVA did. I found a big part of the story and the humor was the innuendo of incest. Like the author saying: "I'm gonna go the incest route, hehe, watch me do it!" To which the viewer, or at least me, responds: "NOOOO, don't do it, please don't go there!!" After that the author just laughs in the viewers face going: "Nah, just kidding, LOL, you fell for it OLOLOL!" And in the end, he does and doesn't. That's the worst part of the whole OVA in my opinion. First Kyousuke shoots all the other, more likeable, girls down and settles for the annoying tsundere, which I really don't approve of. However, when the OVA hit the marriage part, I was actually starting to get interested where the author was going to go with this, since the whole setup with the church and kirino's wedding dress showed, that they weren't just fooling around! But, moments later, kirino says: "Let's end it here, as we promised." So, instead of sticking to his guns and writing a story about incest, something very controversial, the author just hightails out! Like, what the F. How can you have kyousuke reject all the other girls, settle for the tsundere in an incest relationship, only to then jump ship?! If your gonna have kyousuke reject everyone for kirino, then AT LEAST stick to it. But no, nothing happens and they just go back to the status quo.