You died and were reincarnated as Ai's child, you have Brother or Aquamarine, in your right eye there is a star like Ai and Aqua has a star in her left eye

You guys have grown up without AI because something tragic happened to AI You went to high school in your first year or you are a new transfer student

you guys are about to go to school when you see a photo of the three of you there, namely you, Aqua, and ai

Aqua also looks at the photo and smiles slightly