Hikaru Ichibanboshi is a second-year student at Kanenone Gakuen, an all-boys boarding school isolated in the Japanese countryside. His name, meaning "number one shining star," directly reflects his self-image as a charismatic and successful ladies' man. In reality, he is a core member of the "Baka Trio," a group of three close friends known for their perverse and comedic antics, alongside the de facto leader Tadatomo "Bacchi-Guu" Ijuuin and the gentle giant Taizo Tenjin. Within this group, Hikaru is characterized as a "yes man" who generally follows along with the group's schemes, though he does have his own ideas for pursuing girls. He is portrayed as slightly more down-to-earth than his friend Bacchi-Guu, but not by a significant margin.

Driven by an overwhelming motivation to interact with and win over the female students who arrive for a one-month co-educational trial, Hikaru styles himself as a suave Casanova. His primary method of seduction involves meticulously deploying pick-up lines from a book authored by a certain "Dr. Tanaka," a tactic that consistently backfires and results in public embarrassment rather than romantic success. Despite his persistent and often clumsy efforts, he is considered the least perverse member of the Baka Trio. His specific romantic interest is directed at Futaba Kutsuki, a strong-willed and independent girl who has a deep-seated hatred for men and flatly rejects all of his advances. This dynamic often leads to Futaba being the one to deliver violent retaliation against the trio's intrusive and poorly planned tactics, such as distributing overly personal questionnaires to the female students. One notable personality trait is his "weak character," which ironically draws him towards someone as forceful as Futaba.

Hikaru's role in the story is strictly secondary and comedic. He serves as comic relief, supporting the main protagonist Yuusuke Takazaki, who is often unfairly blamed for the Baka Trio's misdeeds. When he is not participating in the trio's fruitless schemes, Hikaru has a lesser-known side as a rock and roll guitarist with a band of his own. In terms of character development, Hikaru remains largely static throughout the television series and its related adaptations, including the original visual novel and the PlayStation 2 versions. The official media provide no additional backstory, family history, or substantive evolution for his character, and he appears in the OVA "Green Green Thirteen: Erolutions" in a consistently secondary and comedic role.