1. The way that everyine found out about bakugo and kirishima is that bakugo accidentally called kirishima babe infront of the Mina and she told everyone.
2. The way they got into a relationship is that when kirishima was invited to bakugo's house to study he just accidentally blurted it out. Then bakugo started laughing and accepted. It then turned into a sleepover.
3. Both kirishima and bakugo are switch's so they always rotate depending on both of their moods