Kana doesn't care about her tragic past because she's happy with Daikichi now. She tells Daikichi that her prior life doesn't really matter much anymore when he asks if she ever wonders who she was.
Likewise Daikichi is too busy thinking about his future with Kana to dwell on the unfortunate circumstances that brought him to this point in his life. Early on, he mentioned that he'd rather not talk about it, and he never does, except to eventually admit to himself that he's thankful for those terrible events because he never would have met Kana otherwise.
Utako's only-hinted-at back story sounds horrifying, but, like Daikichi, she never mentions it. Instead she gets inspiration from her new friends to keep going forward with her music and by the end she is working on recording her own CD.
Inagawa sports the most angst of anyone, being depressed over his mundane life compared to his love of the occult. However his date with Kana gives him the "paranormal" experience he's wanted his whole life and is able to return to his daily routine satisfied, happy, and with a renewed enthusiasm for both life in general and his specific obsession with the occult.
Big-Lipped Alligator Moment: The chapter following two random characters, stuck at a hotel, during a storm. They are never hinted at before, and never appear again after the chapter.
Periphery Demographic: While some angle choices during the love scenes can occasionally remind you that male readers are the primarily targeted audience, everythingelse makes it a very enjoyable read for male and female readers alike. Including the very cute Daikichi.
The Woobie: Everyone to some extent but Utako is easily the most in need of caring friends. She has had something horrible in her past that you don't know if it would be better to know or not. Either way you just want her to be happy soooooo much. Thankfully she gets there.
Daikichi.