Yuyu wants to give Riri a birthday present but doesn't know what to give her. While Riri struggles to find two more members for her legion, can Yuyu overcome her awkwardness and find a way to cheer Riri up?

Riri finds a mysterious girl in the remains of a dead Huge. The amnesiac girl quickly grows attached to Riri, who devotes herself to taking care of her. But just who is this girl, and how will Riri's legion deal with her absence?