Undohkai is a Daimon Heart Snatcher sent by Mimet to steal Pure Hearts. She has a giant crab shell on her back (as she was created from a shell) and can shoot ribbons that tie people together. She appeared in Sailor Moon S Episode Preview 28, Heightened Hazard.
Mimet took Undohkai with her to extract the Pure Heart of an athlete named Shawn Hayes. After sucking out his Pure Heart and eating it, Undohkai attempted to run, but ran into Hotaru,who she thought was injured and advised Hotaru to go to the medical room, looking up at her she blasted Undohkai backwards, She was protected by her shell, but Sailor Mini Moon used Pink Sugar Heart Attack on her, and Sailor Moon transformed into Super Sailor Moon and destroyed her with Rainbow Moon Heart Ache, leaving only the shell and Shawn's Pure Heart.
- She may be the most sympathetic Diamon of all due to stopping for Hotaru while she was running away to help her out.
- Hotaru may have blasted Undohkai because during one of her attacks Hotaru's letter to Shawn burned up in the attack this may have happened as revenge.