Aoi Seimoto is a supporting character in the romantic comedy series Rizelmine. She is a classmate of the protagonist Tomonori Iwaki and is part of the same school environment where the main story unfolds. Physically, Aoi is an adolescent girl with brown eyes and brown hair that reaches approximately neck-length, often styled in a way that includes a distinct ahoge, or cowlick, and she is typically seen wearing her school uniform complemented by a bow.

Within the social circle of the school, Aoi occupies a specific position in the complex web of unrequited affections that drives much of the series' humor and conflict. Her primary role in the story is defined by her romantic interest in another classmate, Ryunosuke Hououin. Ryunosuke, however, is famously obsessed with Rizel, the young genetically engineered girl who has been forced into an arranged marriage with Tomonori. Specifically, Ryunosuke's fixation is often comedically centered on Rizel's signature bear-print panties, making him largely oblivious to Aoi's feelings. This dynamic places Aoi as a key participant in the show's "love dodecahedron," where her affections are one of several that go unreturned for the majority of the narrative.

Aoi is characterized by a cheerful and spirited personality. She is known for her energetic and somewhat eccentric behavior, which includes a notable quirk of calling out her attacks in a manner reminiscent of characters from fighting games, similar to Captain Falcon. This adds a layer of playful, action-oriented comedy to her interactions. Despite her friendliness, she is not the primary object of Tomonori's attention. Tomonori, whose most defining trait is his preference for older women, does not show romantic interest in Aoi, who is close to him in age. Instead, his affections are initially aimed at their teacher, Natsumi Ibata, and later evolve toward Rizel after he discovers her true age and identity.

The character arc for Aoi, along with the other supporting characters, finds resolution in the way the series handles its many romantic subplots. The narrative employs a "Pair the Spares" trope to resolve the various unrequited loves that have built up over the course of the story. In this resolution, Aoi ultimately ends up happily paired with a dog, a bizarre and comedic conclusion that fits the series' offbeat tone. This development underscores the show's tendency to prioritize absurdist humor over conventional romantic resolutions. As a supporting character, Aoi Seimoto contributes to the chaotic school-life setting and the tangled romantic relationships that complicate Tomonori and Rizel's central, government-mandated union.