Prim (プリム, Purimu) is the fiancée of the Prince of the Underground who hoped to become Lum’s new groom.
Prim is presumably a succubus with red hair, grey horns, black wings, bikini, wrist/neck band and boots.
She seems to have a rough personality, with low tempered characteristics.
Heavily disguised and with a male voice, she forms an anti-matchmaking front to disrupt a party, in which her fiancée was invited, that was organized by Lum's Father in the hope of finding a new groom for Lum. She had already recruited Ataru and Ten and then recruits Diana who is saddened by her fiancée Yuni about to become Lum’s new groom. She had Ten inspect the ballroom only for him to blab about the disrupting plan and consequently let everyone know which causes Lum’s father to announce Lum being engaged to Yuni, so she and her comrades show up getting Lum and Yuni on their side and as they were surrounded by guards and about to fight them, the Prince of the Underground emerges from a hole underground to which they make their escape. She instructs him to dig deeper then gets mad at him for chasing Lum and takes off her disguise to make him remember who she is, only to be further annoyed by the fact that he claims having not forgotten her and have Ataru jumping over her back much to her disgust. She gets further annoyed by her fiancée when he leads everyone back to Lum’s father who however agrees to cancel the party, and takes him back home while warning him that she’ll kill him if he runs away again.
- Prince of the Underground: As his fiancée, Prim doesn't seem to like him, and scolds him for every wrong move he does. The Prince apparently, ditched her on their honey moon which she reminds him of in Lum-chan's Class Party.
- Prim was actually the result of a fan contest creation for the manga, Design a friend for Lum and was chosen as the winner. She was drawn by Yamaguchi Tetsugo who was 16 years old.
- She is voiced by Machiko Washio who voices Sakura.