OVA
Description
Kouhei Ueno is a supporting character in the series Nazo no Kanojo X. He is a second-year student at Kazamidai High School and a classmate of the protagonist, Akira Tsubaki. Ueno is often seen wearing glasses and has an ordinary appearance that does not stand out. He is a close friend of Tsubaki and is one of the few people aware of Tsubaki's unusual relationship with Mikoto Urabe.

Ueno's background includes a secret romantic relationship with Ayuko Oka, a girl from another class. The two have been dating since the winter of their first year of high school, roughly a year before the events of the story. Their relationship is kept hidden from most of their classmates, and only Tsubaki, Urabe, and later Hayakawa are aware of it. Ueno initially asks Tsubaki to keep their relationship a secret, as he is somewhat apprehensive about it being known.

In terms of personality, Ueno is generally mild-mannered and friendly. He often fondly recounts his experiences with Oka to Tsubaki, who in turn gains romantic ideas from Ueno's stories to use with Urabe. However, Ueno also displays a noticeable jealous and possessive streak, particularly when it comes to Oka. He does not like the idea of other boys seeing her in a revealing swimsuit and becomes jealous when other guys talk to her. This protectiveness is a key aspect of his character.

Ueno's primary role in the story is as Tsubaki's best friend and a source of romantic advice, albeit indirectly through his own stories. He serves as a foil to Tsubaki, offering a more conventional perspective on dating and relationships. His secret relationship with Oka also mirrors the more mysterious and unusual bond between Tsubaki and Urabe, providing a contrast. Ueno's motivations are centered on maintaining his relationship with Oka while navigating the typical anxieties of a high school romance, including secrecy, jealousy, and the desire to keep their bond private.

His key relationships include his friendship with Tsubaki, which is built on mutual trust and shared secrets, and his romantic involvement with Ayuko Oka. Ueno and Oka's relationship, while kept hidden, is depicted as genuine and affectionate. The exact circumstances of how they got together are not fully detailed, but it is mentioned that they became close and began dating after walking home together.

Throughout the series, Ueno's development is subtle. He remains a steady and supportive friend to Tsubaki while continuing to navigate his own relationship. His possessive tendencies are a consistent trait, but they are presented as part of his character rather than a flaw he overcomes. In terms of notable abilities, Ueno does not possess any supernatural or extraordinary talents. His significance lies in his role as a confidant and his function as a representation of a more typical high school romance within a story centered on a very unconventional one.