Kiriko has violet eyes and light magenta hair, with part of the latter styled into a pair of small buns. She wears the standard dress shirt of Hope's Peak Academy and a dark gray/black skirt with white undergarments. She also wears a red headband with a bow on top of her head.
Kiriko is seen to be scared and quite silent during the beginning of the killing game, though still appearing relatively calm. Later, she is shown screaming and running towards Sōsuke as she tries to kill him, presumably acting out of panic, desperation, and despair.
Kiriko was summoned by Junko Enoshima late at night in Hope's Peak Academy's old school building along with the other members of the Student Council. It was revealed that she and the other members were lured by Mukuro Ikusaba and Junko by using a threatening video for each individual. From the beginning, Kiriko is shown to be scared and confused by the current situation that she faced.
Soon after the Killing Game started, Kiriko picked a shovel as her weapon and tore down the corridor in order to murder Sōsuke. Before she could murder her, Sōsuke stabbed her abdomen, leaving her to slowly bleed to death.
Sōsuke was Kiriko's friend. During the killing game, however, Kiriko attacked Sōsuke out of fear and was killed by him. Sōsuke showed much remorse over killing Kiriko, asking why she made him do it and confessing he loved her. His words imply he never told her about his feelings and it's unknown how she felt about him.
- Her given name, "Kiriko" (桐子) means "paulownia child".
- Her last name, "Nishizawa" (西澤) means "west stream".