Well, the song has no great connection with the plot except that it's one of the favourite songs of Naoko, a girl with some psychological problems and a tragic love of Vatanabe, the main hero. The book is full of song-mentioning, which is sometimes tiring if you do not know the titles, but which also adds some nostalgia to the book.
Vatanabe, being 39 and living abroad, is remembering his youth at the university and his difficult relationship with Naoko. Now, everything is difficult here, because for her whole life she was a girlfriend of Vatanabe's friend, who committed suicide when he was 17. Because of this and because of other family problems she has some mental problems, and her developing relationship with Vatanabe is making it worse. Meanwhile, Vatanabe is studying at the university, ignoring political life around him, making strange friends and trying to decide what to do with his life.
The book is full of sex, suicides and strange, sometimes overdone pathetic feelings. But, strangely enough, it doesn't irritate me here. Usually when I read about some teenagers talking tragically and ruining their health and lives because they are so unhappy and everything, I want to shake them and say "Don't be idiots, please!", but maybe due to the overall mood of the book, all this was quite bearable here. And sex... Well, I had fun guessing when and with whom the main hero will have sex next. It's easy: he never misses a chance =)
All this said, the book is very easily read, it just flows by as you say "Hello!" and "Goodbye!" to different characters that get involved in Vatanabe's life. So I rather enjoyed the book, and I wish I read it when a teen, without some skepticism which I can't put aside now. Recommended to those in a mood for some tragedy and strangeness!