Rideru Takatsukasa
Voiced by: Marina Ohno
Rideru
Protagonist.
- Babies Ever After:Canonically, she had children from both Tomaru and Kuu.
- Childhood Friend Romance: Can have this with Kuu in one of the routes. Canonically, she succeeds.
Kuu Hazama
Kuu
Another one of Makoto's half-brothers and Shun's full brother, he is the youngest of the Hazama siblings.
- Abusive Parents: Averted. His mother was loving, and he has, to date, the least problems with his father of all his half-brothers, Tomomasa and Youji aside.
- Only Sane Man: The only one of Tomaru's illegitimate children who has not had a particularly insane life and seems to, for the most part, be perfectly stable, incest aside.
- Really Gets Around: Completely averted in his case. Kuu is only (possibly, official continuity is still somewhat muddy, but the official incest chart confirms it) confirmed to have a child with Rin (one of Kagura and Tomaru's daughters), Rideru Takatsukasa (Arisu and Tomaru's daughter), and Rika (Tomaru's [grand]daughter with his daughter Risa). By some miracle of fortune, he seems to have avoided the wanton sleeping around of his half-brothers. That being said...
Rin Inou
Voiced by: Shiho Hisajima
A heroine. Rin was also a character that appeared in Stack's Sister Princess visual novel, and was referred to as "Rinrin".- Babies Ever After: Canonically, she had a child with Kuu.
- Brother–Sister Incest: Kuu is her half-brother.
- Chuck Cunningham Syndrome: Much like most of the cast of this game (except Tomaru), she doesn't reappear after Summer Radish Vacation and isn't even mentioned.
- Transplant: As noted above, she originally appeared as a character in Sister Princess before she joined the cast of Summer Radish Vacation 2.
Rika Inou
Voiced by: Sayaka Aoki
- Absurdly Youthful Mother: Rika is the youngest character in the 0verflow universe to-date to become pregnant.
- Abusive Parents: One word: TOMARU.
- Babies Ever After: Canonically, she had children from both Tomaru and Kuu.
- Brother–Sister Incest: Kuu is her half-brother.
Sayura Kusumoto
Originally a character from Witch's Milkyway and it's sequel, Milkyway 2.- Babies Ever After: In one of the endings, Sayura gives birth to a baby girl from Kuu.
Risa Inou
Rika's mother, and Rio and Tomaru's daughter.- Absurdly Youthful Mother: Same as her mother, grandmother, and great-grandmother. She's also seen pregnant with her second child in a picture along with her pregnant mother.
- Parental Incest: Born from this, subject to this.
Wataru
Rin's brother. Wataru was also the main character from Stack's Sister Princess visual novel.- Connected All Along: In this continuity he was born from Kagura having been prostituted to the school principal.
- Transplant: As noted above, he originally appeared as a character in Sister Princess before he joined the cast of Summer Radish Vacation 2.
Hinako
One of Wataru's sisters. Hinako was also a character that appeared in Stack's Sister Princess visual novel.- Child by Rape: In this continuity, she was the result of Wataru being forced to rape his mother Kagura.
- Strong Family Resemblance: Looks like a younger Kagura.
- Transplant: As noted above, she originally appeared as a character in Sister Princess before she joined the cast of Summer Radish Vacation 2.
Yotsuba
One of Wataru's sisters. Yotsuba was also a character that appeared in Stack's Sister Princess visual novel.Jou Inou
A millionaire and former owner of the Radish franchise. Also the father of Moegi and Asagi Inou, as well as Tomaru Sawagoe- For Want Of A Nail: The events of 0verflow's games probably wouldn't have happened if not for his dalliance with his mistress.
- He Who Must Not Be Seen: Has yet to appear in any game and is only mentioned by name.
- Small Role, Big Impact: One word: TOMARU
- Strong Family Resemblance: While he hasn't physically appeared yet in any of 0verflow's games, Tomaru apparently looked so much like him that Mrs. Inou could tell at a first glance, that he's Jou's son.
