Jin Koishikawa 小石川仁

Miki's father and an accountant who works at a bank. He married Miki's mother Rumi after breaking up with his old girlfriend Chiyako and helping Rumi over her own break up with her boyfriend Youji. They moved to England and had Miki there, then returned to Japan. Later, he and Rumi reencounter Chiyako and Youji, reach an agreement, and swap spouses