- Name: Keiko (恵子)
- Classification: Human
- Homeland: Japan
- Age: 14
- First Appearance: Manga Chapter 76, Anime Episode 5
- Seiyu: Ai Nonaka, Kerry Williams (English)
Keiko is one of the best friends of Rinko Nikaido. In the manga, she is bullied by Tamaki in school, and almost ended up dating The Rigani for money so she could pay off the bullies. Rinko steps in to stop her, which leads to The Rigani fighting Kinniku Mantaro. In the anime, she appears with Rinko and Tamaki during the Tel-Tel Boy fight, and in the same episode, Mantaro mistakes Rinko calling out to Keiko as cheering. During Mantaro's fight with Check Mate, Keiko realizes the one vote called in for Mantaro was by Rinko, which Rinko denied. Along with Rinko and Tamaki, Keiko cheers on Team AHO for the majority of the anime and manga. She is the second hostage up for grabs in the Poison Six Pack Arc, and she is saved by Gazelleman and Seiuchin, with Seiuchin catching her.
In the Ultimate Chojin Tag Arc, she stayed behind with Tamaki. It's unknown if these two know Rinko snuck on board the time ship.