by Kaho Miyasaka It's the proverbial teen love cha-cha-one step forward, two steps back - and they dance to the beat of their own hearts. Old-fashioned curiosity propels Karin to the sexual frontier, but the little girl inside her holds her back. In the case of Karin and Kiriya, Karin's hesitation to have sex has been the cause of their most bitter quarrels, but nothing could have prepared these troubled lovebirds for the Valentine's Day drama that loomed ahead. Rating: T