Rival-chan exists because at some point in 2015, YandereDev was not satisfied with her appearance as the original Osana Najimi. This version of Osana "didn't look tsundere enough", so Osana's old appearance became Rival-chan. Rival-chan currently remains in the game as a placeholder model, as she is not fully implemented, while Osana has a new appearance and retains her tsundere personality.
Rival-chan is an extremely short girl, and is currently the shortest character in the game. She has flushed cheeks, a soft smile, orange-amber eyes, and pale skin. Her ginger hair is worn in two slightly curled pigtails. To keep her hair up, she wears ruffled pink and white polka-dotted scrunchies and a purple ribbon. She wears the default female school uniform, unless customized by the player, and black shoes with white loose socks.
She is highlighted red in Yandere Vision.
Rival-chan does not have a programmed routine. In April 2015, YandereDev said that she would walk around, but that was before Osana's original appearance became Rival-chan's. She currently stands by the closest cherry tree to the left of the fountain in the plaza.
YandereDev calls her "indestructible", as apparently many players have tried to kill her to no avail.
She appears in the spin-off game Yandere Clicker back when she was named Osana Najimi. Her face was used for the "Imouto" option, described as "A kawaii Imouto who will stab Senpai for you". However, she is not Senpai's sister and should not be mistaken as such. She also makes a small cameo in the "April Fools Parody Trailer", where her photos appear on the corkboard. Knives through Rival-chan's head hold the photos up.
She makes another cameo in "It's Beginning to Look a Lot Like Murder", where Rival-chan was hunted down by Yandere-chan through the woods and eventually killed.
- She is unaffected by any Easter Eggs or the Demonic Ritual.
- She is the only unprogrammed NPC whose uniform will change according to the player's choices.
- Before the November 15th, 2015 Build, she always stood by the first cherry tree by the school entrance. She was moved to the plaza in the November 15th, 2015 Build.
- Pressing Space will make Rival-chan cycle through several animations.
- She makes multiple cameos in the Challenges Menu, where she is shown as the target of every elimination method.
- Rival-chan's 3D model is available on the Unity Asset store, and her model is named Satomi Makise.
- Her hairstyle cannot be loaded by any other NPCs.
- As of the September 1st, 2017 Build, players can now load students with her hairstyle.
- Rival-chan makes a small cameo in the Gaming Club by appearing on the stealth game, being stalked by Oka Ruto.
- The reason why her hairstyle was added into game files JSON and Pose Mode was because a fan wanted to pose her.