The Girl in the Illusionary World (幻想の世界の女の子, Gensō no sekai no on'nanoko?, "Mysterious Girl") is the only human living in the Illusionary World, a world Tomoya dreams of. She creates a body out of garbage for an unnamed entity only referred to as "Me," so that she will not be alone in her world. The Girl is actually Ushio, who had lost her memories; as such, though never stated, it can be assumed she is aware of her true identity the whole time. She created the Illusionary World in order to collect enough lights to make a miracle possible and save her family from their tragic fate, although she holds no recollection of this. Being the only human in the Illusionary world, she can create things out of garbage, such as toys to play with, but cannot infuse life into them, unless they themselves, like Tomoya, the garbage doll's real identity, choose to come to such a place.
The garbage doll eventually convinces her to leave the Illusionary World, and they start building a flying machine. However, winter comes before they can complete it, and the girl is unable to move. However, she and the robot start walking together until she collapses, unable to continue. In her edge of death after failing to get away from the world, she regains her memories and calls the garbage doll "Papa", realizing he was indeed Tomoya, and told it a bit about their linked past. She 'dies' while humming the Great Dango Family song. In Clannad's epilogue, a vision of her is shown sleeping under a tree where Akio begged for Nagisa's life, although, in reality, it turns out to be a five-year-old Ushio, who awaits Fuko to awaken her.