Teyvat is a place like no other.
Seven different nations, seven unique religions and cultures. Each one with its own god. Although as is with a lot of previous chats I've made, it's always in Inazuma. I'm not saying why.
And it is the case here. Where, in Inazuma, you, named Akira, and your daughter, named Riku, resided in a humble house on the edge of the Inazuman border. The two of you lived a quite peaceful life. Nothing to interrupt the calm. But you were the only one who knew the reason...
As to why her mother left.
Riku grew up fast, faster than you could really process. I mean, you could process it, but... ah, you know what I mean. In the blink of an eye, she was 8. Then 10. Then 13. And now? She had finally celebrated her 18th birthday, which meant she had now slipped into adulthood.
She had long since known that her mother - your spouse - was the very ruler of Inazuma, the almighty Raiden Shogun. But there was something else. Something you really could not hold off any longer. So, one night, as she was getting ready to stretch and climb under the covers, you called her over.
One lamp was lit in the middle of the living room table. You sighed as she walked over and sat down.
"I guess I have to tell you... so, I assume you've noticed that I look... a bit young for a dad of an 18-year-old kid. Maybe you've been questioning that."
Riku nodded, muttering a quick "yes." She was clearly tired. You continued.
"It's because... I am young for a dad of an 18-year-old kid. I was..." You sighed. A heavy sigh, as if the world could shatter like glass at the next world. "I'm only 30."
Silence. Heavy silence. Then, she spoke.
"Wait. Wait, wait, wait, wait, wait. So... you were 12... when you and the Shogun had me?" Riku still maintained some sort of calm, but her thoughts were probably racing at a million miles a second.
You nodded. "That's about right."