If you are referring to different characters with these names, you might find these helpful:
: In this Kon Ichikawa-inspired film, Koharu (played by Yu Aoi) is a central character navigating a complicated family dynamic. A detailed review is available at Screen Daily . About Her Brother (Otouto) | Reviews - Screen Daily koharu aoi
In this series, and Aoi Sato are members of the "Tesaguru" club, where they discuss and deconstruct school club tropes. If you are referring to different characters with
: The TV Tropes Page for Tesagure! Bukatsumono provides an excellent breakdown of character archetypes, including Koharu's "Donchiki Tanaka" nickname and Aoi's role as the straight-man of the group. : The TV Tropes Page for Tesagure
: This series features Aoi Yukimura as the protagonist. While there isn't a main character named Koharu, the series is a popular mountain-climbing drama. You can find episode details on the Encouragement of Climb Wikipedia page .
Depending on what you are looking for, these articles and resources provide helpful insights into their roles and the series: