- Classification: Human
- Homeland: Japan
- Age: 14
- First Appearance: Manga Chapter 74 Anime Episode 5
Rinko is the adopted daughter of Mari Nikaidō and is Mantaro's love interest. She attends Private High School, Class 2-A. In the original manga she is a kogal and debuts after the Hercules Factory Second Year Replacement Matches, but in the anime she is a more wholesome high school girl who loves wrestling and first appears during the Tel-Tel Boy fight. Her two best friends are Keiko and Tamaki Maekawa and they are almost always seen with her, although lately they have been fading into the background and she has been spending more time with Jacqueline. Although she occasionally seems more interested in Jade or Chaos, she is generally considered Mantaro's girlfriend.
She refers to Mantaro as Manta. In the Japanese version, she and her friends refer to Seiuchin (Wally Tusket) as Sei-chan.
Prehistory, The Rigany, Choujin Olympics: The Resurecction and Poison Six Pack (anime only)
After the Chojin Crown prelims are finished, a group of Akugyou Chojin known as the Poison Six Pack kidnap Rinko, Keiko, and Tamaki as hostages for the upcoming tag matches held around Mount Fuji. All three girls are held in a floating jester head, wearing skimpy tarzan colored bikinis (these outfits are censored in the dub). Tamaki is the first hostage held in a glass capsule, hanging off a part of the jester head. If Team AHO lose a tag match, the girl held in the capsule become's the Poison Six Pack's slave.
During the first match, Terry the Kid and Jade vs. Dazzle and The Protector, Rinko and Keiko shout encouragement to a scared Tamaki, as Kid and Jade are being pummeled by the first two members of the Poison Six Pack. After Tamaki is freed, Keiko is the next girl up for grabs. With encouragement from Rinko, Keiko and Gazelleman, Seiuchin dives into the lake to save his mother and sister. As Mantaro fights Baron Max-a-Million, Suguru uses Roxanne as encouragement, saying things like her being Mantaro's future wife, which pisses off Rinko to no end, making her freak out in her glass capsule. Near the end of the fight, Mantaro nearly hits Rinko's glass prison, holding onto the ring ropes to set up a massive Muscle Millenium. With Baron defeated and Mantaro victorious, everyone is bewildered as to why Rinko's glass capsule hasn't been released. Baron, in his final moments, makes the jester head explode, sending Rinko flying over the edge of Mount Fuji's crater. With Rinko safely in Mantaro's arms, the two are still falling off the edge, and are saved by Team AHO. Both Rinko and Mantaro humorously knock Gazelleman back into the crater.
Rinko, who is supposedly about to kiss Mantaro, quickly makes Mantaro kiss Nakano. Mantaro is mad, but Rinko says he was giving her the creeps (according to the dub). However, as she whispers "Truth is, I love-" the jester head explodes and drowns out the last part of the her sentence. Rinko skips away as Mantaro tries to make her repeat herself.
Demon Seed Arc and Ultimate Choujin Tag Arc
- Birthdate: September 9
- Theme Song: "Go, My Boy!" by Fumiko Orikasa, Reiko Kiuchi, and Ai Nonaka
- Shirabara High School Student