Yuitsuka has neck-length dark brown hair. She also has dark grey eyes. According to Jin, she has a pretty face.
Karin is a grumpy girl, as demonstrated by her when Jin came to the base. Not much of her personality was shown in the manga, but in the anime she was shown to be rather grumpy, and annoyed of Jin. Later, she is shown to be very serious and dilligent, but get easily flustered and angry when teased.
At one point in the past, she was part of an unit led by Azuma.
- "Karin" is written with 夏 ("summer") and 凛 ("cold"), while "Yuitsuka" (結束, usually read as kessoku) means "unity".
- Like the rest of her teammates, she was originally a character of Room 303.
- Her voice actress, Kozue Kamada, also voices Izukacha and Yuka Kon.