|“||Look...aren't they cute? They're my everything.||”|
–Rei Shimizu talking about her parasites, Danganronpa Gaiden: Killer Killer
Rei is a thin, young lady with messy black hair placed in a ponytail, and large dark eyes. She wears a white nurse dress, white nursing shoes and a long sleeved black jacket. She also has a white nurse's cap and a name tag that states her name. Underneath her clothes she wears a black tank-top. She is infested with multiple parasites.
Rei, at first, acted very sweet and a bit clumsy. She was very kind to her patients and does her job sufficiently. However, Rei's true personality is different, Rei acts very deranged and gets less patient, as shown by her reaction to Takumi's point system. She has an obsession with parasites and constantly fawns over them, inserting them into her patients and herself to help them grow.
Danganronpa Gaiden: Killer Killer
Chapter 2 - Symbiotic Hospital
Rei was a suspect in Hana's murder case. When she was called to the SCI interrogation room, she clumsily tripped before she introduced herself. Takumi, a member of SCI suddenly has a serious heart attack when he looked at Rei for the first time.
After Takumi regains consciousness, he disappeared from his room in Ongou Hospital, making Rei who was about to take him to exam room, panicked and searched for him. Eventually she found Takumi who discovered Hana's surgical history in an archive room and asked whether she was Hana's acquaintance.
Later that night in an operation room, Takumi surprised Rei by confessing his love to her, and he also revealed that Rei was the culprit of Hana's murder case. Frightened, Rei ran from Takumi until she arrived in the middle of a forest. However, Takumi managed to chase after her. He said that Rei planted parasite eggs in Hana's body during her operation one year ago.
Rei admitted her crime by revealing parasites she kept inside her body. Before Rei could kill Takumi with her parasites, Takumi immediately performed a kill steal on both of Rei and her parasites, slicing them into pieces.
To prove that he successfully performed a super kill steal, Takumi deleted all of documents regarding Rei and all that's left was her hospital ID card.