Rival-chan was the original character model for Osana Najimi.
However, YandereDev stated she 'just didn't look Tsundere enough', so Osana was redesigned. She attends Akademi High School for now, but she isn't active, unlike other students. When the actual Osana is implemented, the character will be removed. Her model, however, might be used in the game.
Rival-chan wears the default school uniform, as well as white-style leg-warmers. She keeps her orange hair in pigtails with pink and white polka-dotted scrunchies. Her eyes are also colored orange, and her skin is pale with a yellow tone. She has rounded blushing cheeks. She is the shortest character in the game. Her bust is bigger than Ayano Aishi's.
She stays below a cherry tree in the courtyard all day, as she is an "inactive" student. This causes her to have no actual routine other than standing there.
Satomi Makise is the character model that represents Rival-chan. Satomi was also used to represent Imouto in Yandere Clicker.