Mai Motoki is a supporting character known for being one of the closest friends of Kokoro, the female lead. As a classmate and confidante, Mai is consistently seen alongside her friend Aki Kagami, and together they form Kokoro's primary social circle at school. Mai possesses a personality that is notably serious and straightforward, distinguishing her from some of her more energetic peers. While she shares a level of maturity with the reserved Kokoro, she is not as inwardly focused; instead, she is known for being more openly expressive and direct in her reactions, particularly when it comes to matters she feels strongly about.

Her primary role in the narrative is tied to her protective stance over Kokoro. Mai is deeply invested in Kokoro's well-being and acts as a vigilant guardian of her happiness. This protectiveness manifests most clearly in her attitude toward Kippei Katakura, the male protagonist and Kokoro's love interest. Due to Kippei’s established history as a carefree playboy prior to taking responsibility for his young cousin, Mai does not easily trust his intentions. She frequently reacts with visible frustration or anger toward him, especially when he behaves in a thoughtless or insensitive manner that might hurt Kokoro. Mai is often the one to voice sharp, critical words to Kippei, making her disapproval clear and serving as a narrative obstacle that he must overcome to prove he has changed.

Despite her harsh exterior toward Kippei, Mai’s motivations are rooted in sincere friendship rather than malice. She is not merely a busybody but a loyal friend who genuinely wants what is best for Kokoro and is wary of anyone who might cause her pain. This dynamic establishes Mai as a key figure who helps ground the story’s romance in a realistic social context, where friends are naturally protective and skeptical of a newcomer with a questionable reputation. Her notable ability lies in her emotional honesty and her willingness to confront conflict head-on, speaking her mind without the hesitation that Kokoro often exhibits. While she is a secondary character whose personal life and development are not deeply explored, her consistent presence provides a necessary counterbalance to the developing relationship between Kippei and Kokoro, reinforcing the central theme of earning trust and proving personal growth.