|Appearance||Period 50: Friend of the Science Room|
Yuu is a young girl with long hair worn loose, with straightened bangs and her ears covered by hair. She wore a flower hair pin on the corner of her bangs.
Not much of Yuu was known, other than her seeing no harm in stringing along girls who were willing to please her and Hana by providing some use to them. When the girl was unwilling then she was fine bullying her.
At the start of the story, Yuu and her friends were discussing the rumor of the skeleton in the Science Prep room, which was said to move after school. She suggested they make Asato enter the creepy room in order to see if the rumors were true, but when Asato refused she and Hana began to lash out at her, deciding to make her take the place of the previous girl they were bullying, Chiba. She and Hana locked Asato into the room after tricking her to step inside, then they abandoned her.
After school, the girls began to make plans to go out for karaoke when Yuu noticed her missing hair pin. Hana and the others went to the restroom after recalling that she had been fiddling with it while they stood outside of the science room, so she heads there to retrieve it.
The following day the class was informed by their concerned Teacher that Yuu was missing. Nobody has seen or heard anything, and when Asato recalled hearing their discussion the prior day, she returns to the science room to search. She locates Yuu's hair pin by the skeleton, but was unable to find her.
Late in the story, Asato began to recall how she would let Yuu and Hana use her for things like copying homework, in order to be liked. This made her realize that they were never truly her friends, and to her horror she eventually discovers parts of Yuu were stitched onto the skeleton, who dismembered her and put her other parts into nearby jars.