In the 8th and final year of the game after the second semester, Hitoshi may propose to your daughter while they are on a date. In order for this to happen, Hitoshi's orb must be at it's absolute highest and Hitoshi's friendship event must've occoured. Also, you must not have triggered any other endings. If you accept the proposal, the two will marry at the end of the game. There are two different endings that one can achieve when marrying Hitoshi, a good one and a bad one. One achieves the good ending by having low sensitivity (under 80), and the bad ending by having high sensitivity (80 and over).
Your daughter will become a busy housewife with five children. Hitoshi will work as a security guard and a cooperative father.
Your daughter will be fed up by Hitoshi's attitude of not helping her with child-rearing, and cannot handle five children. they will break into a fight, and your daughter will storm out of her marriage and come to live with you.