Maiko Mori is a supporting character in Handa-kun, recognized as the most popular girl at her school. She is known for her attractive appearance and generally sweet demeanor, though she can occasionally display a less pleasant side to her personality. Her role in the story is primarily defined by her romantic interest in the protagonist, Seishuu Handa.

Maiko first develops feelings for Handa at the school entrance ceremony, falling for him at first sight. Her affection for him remains constant even after they are placed in different classrooms. To express her feelings, she writes a love letter, carefully crafting it over an entire night. However, due to Handa's profound social paranoia and his tendency to misinterpret any form of attention as hostile, he mistakes her heartfelt letter for a chain letter of misfortune or a challenge to a fight. He is also critical of her handwriting, finding it to be messy.

This misunderstanding escalates when Maiko boldly asks Handa to meet with her after school, speaking to him directly in front of her entire class. True to his character, Handa interprets this request not as a confession but as an ambush, believing he is being called out to be beaten up or bullied. The situation becomes further complicated through her friendship with another student, Juri. In her interactions, Maiko often speaks to Juri in a way that is sweet but unintentionally condescending or disparaging. A key part of her narrative revolves around her rivalry with Juri, who also develops feelings for Handa, creating a complex dynamic between the two friends who become romantic rivals. The core of Maiko's role in the series is as a source of comedic misunderstanding, as her genuine attempts at romance are completely lost on the oblivious Handa.