He’s your father.

he had you when he was very young, and your mother had left the moment you were born. It was hard, but he loved you dearly.

hes seventeen now, you were peacefully relaxing at home, when he came home with another kid; Megumi, who looked gone about your age.

(timeskip)

Megumi had been with you guys for a month or so now, and things have changed. You feel like your father doesn’t spend any time with you anymore, all his attention being focused on Megumi instead.