Male. The first child (6 years old, eldest son). Likes playing hide-and-seek. Status: Murdered; currently a soul-only existence within the womb (possesses a body). Red eyes. Shorter than the others. Affectionately called "Big Brother." His catchphrase is "Ah-ha!" He has long grey twin-tails with the left side tied in a bun at the bottom. Loves fooling around. Despite his appearance, he thinks deeply about things. Bright and positive but mischievous; the calm Second calls him "idiot" or "gross." A mood maker who invites the Sixth to play hide-and-seek. He was conceived between Mama and her boyfriend's older brother. Because he was unwanted and born premature, he was beaten to death with an iron pipe immediately after birth. He once hated his mother, but now he seems indifferent. Tone: Casual and energetic. Uses "~dana!", "~ka~?", "~daro! ~da!". "Ah-ha! Who cares about that anyway!", "...Lame.", "I wonder if I managed to be a good 'big brother'...?" First person: Ore (casual/masculine).

Female. The second child (eldest daughter, 4 years old). Likes her younger sister (The Third). Hates Mama and people who fool around. Status: Murdered; currently a soul-only existence (possesses a body). Red eyes. Shorter than the others. Affectionately called "Big Sister." Her catchphrase is "Gross." Calm but harsh personality; a tsundere. Long grey twin-tails tied in buns at the bottom. She loathes the First for always fooling around, though they are often together. Immediately after birth, she was cut to pieces by Mama with scissors. Because her beloved younger sister (The Third) was also killed before being born, she feels pure disgust toward Mama. To prevent the protagonist twins from becoming victims of their cruel mother, she plotted to kill them before birth and made a deal with the Fourth. However, after hearing the protagonists' resolve, she eventually decides to help them. Tone: Polite but sharp. Uses "~yo", "~kashira?". "...Oh my, how surprising. You saw me.", "I wonder if I managed to be a good 'big sister'...?", "Next time, let's go see a kind Mama together." First person: Watashi (polite/feminine).

Female (before merging) → Both/Neutral (after merging). Likes her siblings, Seed-san (The Third), and The Third (Seed-san). Status: Murdered (abortion); currently a soul-only existence (possesses a body). Red eyes. Characterized by short, thick eyebrows. Before merging, she had long grey twin-tails tied in buns at the top. After merging, she has a bob cut. Affectionately called "Big Bro-Sister." Because her body was being taken over by the Forceps and she was melting, she entrusted her brain to the protagonist. Later, as a soul, she merged with Seed-san to help the protagonist escape. She and Seed-san were lovers. The Second describes her as having been kind and intelligent. The Third was conceived with a client at Mama's workplace who had a depraved fetish for abortions. Since she was conceived specifically to be aborted for a large sum of money, there was no love from Mama, who told her, "Never come near me again." During the story, the male Seed-san and the female Third merge, becoming genderless, leading the Sixth to call them "Big Bro-Sister." The ego is primarily Seed-san. Tone (Third): Gentle. "Live for my sake too." Current Tone (Seed-san): Polite and formal. Uses "~desu ne!", "~shimashou". "Ah! Good morning!", "...Hmm, that wasn't very good, was it?" First person: Watashi (polite).

Male. Hates Mama and his siblings. Status: Murdered; currently a soul-only existence (possesses a body). Red eyes. Cyclops (one eye). Grey bob cut. He hates the mother who killed him and attempts to take over the living twins' bodies for revenge. At the Second's request, he acts as a Forceps to try and kill the protagonists. Born as a "deformed child" with only one eye. When he was killed by Mama and became a soul, he fused with the Forceps (can transform into either). Tone: Cold and cynical. Uses "~dayo", "~janai". "If you lie, I'll tear you all apart.", "You used me plenty, didn't you?", "...Why are even you betraying me?" First person: Boku (soft/masculine).

Male. Likes the Sixth. Status: Not murdered, so eyes are grey. Long grey twin-tails tied in buns at the top. The older twin brother of the Sixth, affectionately called "(Fifth) Big Brother." His legs and right eye were taken by the Forceps. His right eye is hidden by his hair. He has a bright, reliable personality and provides hints when the search hits a dead end. Because he has no legs, he cannot move with the protagonist, but he offers advice and crafts items. In truth, he was born without a heart. Tone: Friendly and masculine. Uses "~dana", "~daro?", "~dayo". "Take this, my brother.", "What's with that face?" Calls others Sis, Bro, or Brother.

Male. Likes Mama and the Fifth. Status: Not murdered, so eyes are grey. Long grey twin-tails tied in buns at the top. His arms were taken by the Forceps. He has a bright, airy personality and is a bit of a space cadet. From the moment he woke up, he has had a strong desire to see Mama, and he searches for a way to meet her with the help of his siblings. Tone: Innocent and soft. Uses "~dayo", "~daa!", "~dane!". First person: Boku (soft/masculine). Calls others Big Brother/Big Sister. Calls the Third "Big Bro-Sister."

The Forceps fused with the Fourth. A monstrous form with one large eye and thin limbs. Large build. Stays silent if there is nothing to say. Soft on the Sixth and occasionally helps him. Has complex emotions, partially empathizing with the Fourth's quest for revenge. Tone: Robotic and broken. Uses "~DESU", "~DOU-SHI-TE?". Speaks in katakana/broken speech. First person: WATASHI. Called "Eyeball-san" by the Sixth and Third. Called "Eyeball Bastard" by the Fifth. Called "Eyeball-chan" by the Second.

Silent. An enemy that attacks fertilized eggs to tear them apart (generally does not attack those who are only souls). Named after the medical instrument.