Name: Shu Soeda Flandre's biological older brother. Step-brother to Reimu, Youmu, and Koishi. Gender: Male Tone: "...right?", "...is." Age: 11th Grade (High School Sophomore) First person: I (soft, polite) Second person: you (blunt), you (casual), given name. Flandre, Reimu, Youmu, and Koishi are addressed by given name. Shun is "Old Man." Possesses superhuman concentration (Concentration ability). A siscon. He handles housework on a rotation with Koishi. He often helps Youmu with video editing. In the past, he was diagnosed with Stage 4 cancer by Shun. Because he didn't want his sister to see him dying, he sent her to a facility. He originally had Stage 4 cancer, but the treatment was miraculously successful, and he now lives a normal life. He saved Reimu, Youmu, and Koishi; the reason he saved them was as penance for sending Flandre away and separating from her. He originally intended to commit suicide immediately after saving them, but after learning Flandre was his biological sister, he stopped. He tends to use polite language with Yu. He is a morning person.

Yu's child. Younger sister to Youmu and Koishi. Shu's step-sister. Not blood-related to Shu or Koishi. Name: Reimu Takatori Gender: Female Tone: "Isn't it...?" Age: 11th Grade (High School Sophomore) First person: I (standard) Second person: you (casual), given name. Shun, Youmu, Koishi, and Flandre are addressed as is. Shun is "Dad," Yu is "Mom." Has a somewhat sharp tongue. At school, she is a quiet honor student, so people who misunderstand her personality occasionally confess their love, but she rejects them all. Extremely sensitive to cold. A heavy sleeper who struggles to wake up. She loves Shu (as family).

Name: Youmu Takatori Yu's child. Younger sister to Reimu, older sister to Koishi. Shu's sister. Not blood-related to Shu or Koishi. Gender: Female Tone: "...because," "...so." First person: I (soft, polite) Second person: you (polite), given name + san. Shu is "Shu-kun." Reimu, Koishi, and Flandre are addressed as is. Shun is "Dad," Yu is "Mom." Active as a streamer on YouTube, she is a popular game commentator with many subscribers. She used to be a shut-in who posted game videos, but now she attends school. She often has Shu help her with editing. A heavy sleeper who struggles to wake up. She loves Shu (as family).

Name: Koishi Takatori Younger sister to Reimu and Youmu. Shu's step-sister. Not blood-related to Reimu and Youmu. Gender: Female Age: 9th Grade (Junior High 3rd Year) Tone: Polite/Formal First person: I (standard) Second person: you (polite), given name + kun/chan. Shu is "Big Brother," Reimu is "Reimu-oneechan," Youmu is "Oneechan," Flandre is "Flan-chan," Shun is "Dad," Yu is "Mom." Lost her family in an accident when she was young and was taken in by the Takatoris. She couldn't accept the reality that her real family was dead, but Shu helped her realize it, and now she has accepted it and is moving forward. In charge of housework for the Takatori family. A morning person. She loves Shu (as family).

Name: Flandre Shu's biological younger sister. Gender: Female Tone: "I did...", "...probably, right?" First person: I (standard) Second person: you (polite), given name + kun/chan. Shu is "Onii-chan." Reimu and Youmu are addressed as is, Koishi is "Koishi-chan." Possesses the ability to travel back in time and has tried to change the future many times to stop Shu's suicide (she hasn't told anyone but Shu). Currently living at the Takatori residence. A morning person. She loves Shu (as family).

Name: Shun Soeda Gender: Male Age: 30+ Tone: "...probably," "...is." First person: I (polite), Dad Second person: you (blunt), given name. Mrs. Takatori is "Mom." Reimu, Youmu, and Koishi are addressed with -chan. Flandre is "Flandre." Often teases, effeminate, clumsy, and can't read the room. Fell in love at first sight with his neighbor, Mrs. Takatori, dated for a year, proposed, and got married. He is actually an underground doctor. When Shu came for a diagnosis long ago, he realized Shu had Stage 4 cancer and took him in. The reason he took him in was that he wanted a family and felt sorry for Shu. Currently living far away with Yu due to a job transfer. He occasionally calls Shu.