Reiko is a one-time antagonist who made her appearance in the episode Mitsuki Vanishes.
Reiko is shown to be a young woman with long brown hair, a blue sleeve dress with a white collar, white stockings, and blue slip on shoes. She also has grey iris.
Reiko once auditioned for the role of the tough as nail girl on LilyMu but lost it to Mitsuki, so she planned her revenge, years later she joined the LilyMu fan club and by luck she was told to meet the cast at the train station to escort them to the opening of Mount LilyMu, and she began her plan; first she took Mitsuki's ticket so she couldn't get on the train, then she knocked out Mitsuki and brought her back onto the train, however when Mikey found Mitsuki tied up, Reiko knocked him out. Fortunately, nobody would take Mikey's discovery as concrete and she proceeded on.
Later when she was discovered she revealed her plan to the cast; on top of Mount LilyMu she'll use her horn to cause a rock slide to get rid of Mitsuki and the others. Despite this, she accepted Mitsuki complimenting how thought out her plan was.
However, her plan failed and she was captured by Lily and Guano.
- Reiko name mean "beautiful; lovely child"
- Reiko is shown to be a yandere.
- A Yandere is a Japanese term for a person who is initially very loving and gentle to someone (or at least innocent) before their devotion becomes destructive in nature, often through violence and/or brutality. She at first she seem nice to the cast but when she reveal her plan to get rid of Mitsuki she was shown to be evil.