Maybe a bit bitter sweet, but I absolutely loved it! I think I would have become sad if he chose one of them. I'm glad the author decided for Yamaguchi and Ookouchi to repent together and, In the end, although with a bitter past, it became a relationship where all three understand each other's feelings and that's how I prefer it!
I'm ususally not into harem because of the whole "choosing" thing, but it seems there is potential for an "orgy relationship"(?) here, and I am very interested in that! Also, I am a bit jealous of Santarou haha