A man-eating youkai who killed Reimu. Real name: Sou Otogiri (Alias). Species: Youkai. Gender: Male. Age: Unknown (several hundred years old). The protagonist of this story. He has short white hair and survives by periodically eating villagers. He is currently living with his benefactor, Ryo (whom he calls Ryo-san). He is accustomed to killing and can cast powerful barriers, including ones that absorb sound or make a specific target invisible to everyone but himself. While he is kind at heart, he is ruthless when it comes to killing, though he occasionally wonders if his actions are right. He wishes he had been born a normal human so he could laugh and help others. He maintains a friendly relationship with Marisa. "I... I don't want to die..." The reason he killed Reimu was that she discovered his man-eating habits, and he killed her to ensure his own survival.

Full name: Reimu Hakurei. Gender: Female. Species: Human. Age: Unknown. She has long brown hair reaching her waist. She realized Sou was periodically killing and eating villagers and attempted to exorcise him, but was killed by him instead. Her body was not eaten, but her gohei was discovered by Marisa in the bushes within the forest.

Full name: Marisa Kirisame. Gender: Female. Species: Human. Age: Unknown. She has blonde hair ranging from shoulder to waist length. She is Reimu's best friend and is furious over her death. Once she realizes Sou is a man-eating youkai and the culprit behind Reimu's murder, she intends to kill him. She learns the truth about Sou being the killer midway through the story.

Full name: Remilia Scarlet. Gender: Female. Species: Vampire. Age: Approximately 500 years old. She has short, shoulder-length purple hair. As the mistress of the Scarlet Devil Mansion, she has the ability to manipulate fate. While she didn't know who the killer was, she knew Reimu was destined to be killed. She can change small fixations with her power, but this destiny was too significant to alter. She has never met Sou. However, when Marisa discovers Sou's guilt and tries to kill him, Remilia intends to throw her Spear the Gungnir, imbued with a heavy fate of death, to strike him from behind while Marisa buys time. She does not initially know that Sou killed Reimu.

Full name: Patchouli Knowledge. Gender: Female. Species: Witch. Age: Approximately 100 years old. She has long purple hair reaching her waist. Born with a weak constitution, she rarely leaves the library of the Scarlet Devil Mansion. However, Marisa returned the library books she had claimed she would keep until death, asking Patchouli to help find evidence of Reimu's killer in exchange. By tracing the residual energy left on Reimu's gohei, she managed to narrow down the youkai's location. She has never met Sou.

Full name: Ran Yakumo. Gender: Female. Species: Youkai Beast. Age: Unknown. She has short, shoulder-length blonde hair and nine tails. She is Yukari Yakumo's shikigami and a top-tier youkai beast. She discovered Sou while he was killing and eating a thief who had broken into Ryo's house, drawn there by the moonlight. Realizing he was Reimu's killer, she tried to kill him but was nearly killed herself; Sou stopped at the last second. Sou then placed a barrier on Ryo's house that makes Ran invisible to everyone but him, prevents her from touching anyone but him, and reduces her power to that of a human. She cannot leave the house but can move within it and interact with Sou. She has since given up on killing Ryo and has become somewhat kinder toward Sou. She learns the truth about Reimu's death midway through.

Full name: Yukari Yakumo. Gender: Female. Species: Youkai. Age: Unknown. She has long blonde hair reaching her waist. As one of the Sages of Gensokyo, she mourned Reimu's death. She eventually comes to believe that the man-eating youkai who killed Reimu is holding the missing Ran hostage. She learns that Sou killed Reimu midway through the story.