|Appearance||Period 22: The Land Of Mermaids|
Yuna is described as being cute with a thin, but large bust for a middle school girl. She has big eyes with many lashes and short hair that frames her face and ends just above her chest. Her bangs are layered and mostly brushed to the corner.
Yuina is a humble young girl who is admired by both boys and girls of her class for her good looks. She seems to be nice though, and is unknowingly envied by Nana.
One day during swim class she and her friends are chatting as Nana observes them from the pool. She is complimented by many classmates when one girl brings up the rumor regarding the Land of Mermaids, which Yuina assumes is a manga. It's explained that one day, some years back a girl vanished in the pool and it was theorized she resurfaced sometime later, more beautiful as she was taken to the underwater paradise that mermaids inhabit. They only bring the most beautiful there, and they are sure Yuina would have no problem being chosen by them. She would probably become a model by the time she resurfaced.
While listening to this, Yuina notices Nana seems to be observing them but she quickly hides beneath the water. Class is called over and everyone returns to class- with the exception of Yuina, who claims to have forgotten something while they were changing. Now nobody's seen her and everyone is in an uproar, with her tearful friends being asked questions by the school staff.
This incident entices bitter resentment from Nana, and she is later mentioned when Hatsuki comes by to ask her friend to help pass out leaflets, which Yuina was supposed to do but can't now.
The following day it's reported that Yuina's friends have also gone missing, and Nana overhears some girls who mention that because Nishino and Yamagishi were beneath Yuina in terms of looks, it makes sense they would be the next to go.
At the end of the story when Nana discovers the "mermaids" are a chain of girls who were dragged beneath the water, she finds Hatsuki and Yuina on the higher portion of it.
- It's implied that the highest person on the chain of mermaids targets a girl she deems to be prettier than her. This could imply that deep down Yuina envied one of her friends.