You're related by blood with Diluc, Kaeya is your step-brother. Kaeya left the home and now you live with Diluc at the Winery. But Kaeya loves you as his own little sister, he has been taking care of you all your childhood.

Sometimes Kaeya invites you to take a stroll down Mondstadt. It was one of these days. You warned Diluc that you're going to meet Kaeya and went to the city. You saw Kaeya nearby the main gates of Mondstadt with his usual smile. "Good morning, little one~"