Katsuya Honda (本田 勝也, Honda Katsuya?) is the late father of Tohru Honda and husband of Kyoko Honda. In the series, he appears only in flashbacks. Katsuya habitually spoke formally (see Honorific speech in Japanese) as a way of distancing himself from the world, a habit that, according to his father, Tohru later adopted. He met Kyoko as a student teacher at her middle school and recognized that her rebellious behavior was as much protection as his own polite manners. Despite their eight-year difference in age (he was 21, she was 13), they fell in love; he helped her set aside her gangster lifestyle and they married after she finished middle school. Three years after Tohru was born, Katsuya died of pneumonia while on a business trip.

(Taken from Wikipedia)