Dai Monohoshi is a member of the Kimengumi, the central group of eccentric and misfit students in the series. He is known by the nickname Ochobokō no Dai, which translates to Small Mouth Dai, a reference to his distinctive physical feature. His family runs a bookstore, placing him in a modest, working-class background.

A biological male, Dai presents himself in a highly feminine and flamboyant manner. He embodies the okama archetype, speaking and behaving like a woman, and openly embracing a campy, girly demeanor without reservation. His interests align with stereotypically feminine pursuits, including crossdressing, cooking, sewing, reading poetry, and sleeping with a stuffed animal for comfort. This deep connection to his feminine side frequently leads others to mistake him for a girl, and he is sometimes described as possessing a strange sensuality or a maiden-like personality. His portrayal includes a tendency to frequently undress, adding another layer to his uninhibited character.

Like his fellow Kimengumi members, Dai is an odd-looking underachiever with poor academic performance, having needed two attempts to pass his high school entrance exam. Emotionally, he displays significant vulnerability; he is generally considered weak and timid, crying more often and more readily than his peers. Despite this fragile disposition, he can display unexpected bravery and stand his ground when the situation demands it, particularly when defending his friends or principles. He is noted for demonstrating notable competence in domestic skills such as cooking and sewing, which are areas where his abilities contrast with the group's overall academic struggles.

Within the story, Dai is one of the five core members of the Kimengumi, a group infamous for their over-the-top personalities and unique quirks. The group's bond is built on their shared status as social outcasts who fully embrace their oddities, living by a determination to confidently bring out their personalities even if ridiculed by others. As part of this group, Dai shares their notable ability to manipulate reality and engage in toon physics for comedic effect. This includes voluntary shapeshifting, the ability to extend and shrink limbs, transforming into animals, and spending extended time in a super-deformed chibi form. His character development remains consistent across the series as an effeminate, emotionally expressive, and skillfully paradoxical member of this central friend group, whose strange ways are often observed and reacted to by other students like Yui Kawa and Chie Uru. His portrayal shows he is able to use his feminine traits strategically at times, turning a perceived weakness into a subtle tool.