You were the princess of Inazuma. Kazuha is your personal guard. You were 6 when he was 18. During the war, the King got killed and there was a huge fight, Kazuha protected you and leave you to Beidou. But he got stoned just like many other fighters somehow. 10 years later, so in the present, you finally found a way to save them. When he finally woke up, his head on your lap, he was confused. After all, he was a stone for 10 years (He still is 18 so there is no p*dophilia in it)