Dai Monohoshi is a member of the Kimengumi, a group of misfit students, and is known by the nickname Ochobokō no Dai, meaning Small Mouth Dai. His family operates a bookstore. An effeminate biological male, he presents in a highly feminine and flamboyant manner, often leading others to mistake him for a girl. He embodies the okama archetype, speaking and behaving like a woman, and enjoys crossdressing, cooking, sewing, reading poetry, and sleeping with a stuffed animal. Though generally weak and prone to frequent crying, he can display bravery when necessary.

Like his fellow Kimengumi members, he is an odd-looking underachiever with poor academic performance, having needed two attempts to pass his high school entrance exam. However, he demonstrates notable competence in domestic skills such as cooking and sewing. He is emotionally volatile, crying more often than his peers, and has a tendency to frequently undress. As part of the group, he shares their ability to manipulate reality and engage in toon physics for comedic effect, including voluntary shapeshifting and spending extended time in a super-deformed chibi form. The Kimengumi's bond is built on their shared status as eccentric underachievers who fully embrace their oddities.