Marriage

Seme's grandmother is addicted to games with bet. She played a game with uke's father and bet her grandson. When she lost, she gave seme to the uke's family.
Although at the beginning of the chapter, uke's parents seems aloof and doesn't care about the uke even when he ran away from home for days. But the thing is, uke's father knows that uke is gay, that's why he asked for seme as the wager so that he can give uke a spouse. What a great father!