Absolutely loved this series! I picked it up after one of my best friends had started reading it and was getting rid of her copies. I thought it would just be something to pass the time, nothing that I would really commit to, but I ended up loving it. The premise is kind of goofy, but it ends up working into a beautifully-crafted storyline. I really connected with Sumire, who was so well-developed and dimensional. I loved seeing her awkwardness, and that contrast between her being shy and attempting to be girly for the man she loves, and her true, real nature of being tough and liking to just kick back and be comfortable.
Momo at first seems like a goofy sort of character. The degree to which he plays along with being Sumire's pet can get a little silly, and would have probably lost my interest if it weren't for the fact that he, too, is a fully developed character. I love that he has his own life that Sumire isn't aware of for a while. I loved watching him change as he began to develop and try to deal with his feelings.
Hasumi is also a great character. It's interesting seeing the awkwardness of him trying to have a relationship with Sumire while she tries to be the woman she thinks he wants. But he's not some cardboard character who is trying to change Sumire. Hasumi himself is a good guy, and although the reader sees everything primarily from Sumire's perspective, you can see that he struggles with the relationship, too.
I have mixed feelings about the ending, though I did sort of bawl my eyes out in the middle of the bookstore when I read it.
I would recommend this series to older readers, as it can get a little mature. As an adult reader, I personally loved that this was about adults and not students. It was great to be able to connect with the characters.