Kobayashi owns BB Lounge, a Shibuya nightclub. His initially intimidating presence often causes him to be mistaken for yakuza, yet he shows deep compassion and support. He possesses a strong fascination with the Three Kingdoms period and enjoys playing Go.

A defining moment saw him rescue Eiko Tsukimi from suicide at a train station, snatching her from the tracks and calling her a "dumb brat" for discarding her life. He brought her to BB Lounge, where singer Maria Diesel's performance reignited Eiko's passion for music. This established him as a father figure to Eiko, with his ongoing support for her musical dreams central to his role. He remains fiercely protective of her emotional well-being, openly warning others against causing her distress.

Impressed by Zhuge Kongming's Three Kingdoms knowledge during an interview, Kobayashi hired him as BB Lounge's bartender and receptionist. While admiring Kongming's strategic mind, he explicitly threatened consequences if Kongming ever betrayed Eiko's trust.

As Eiko's career advanced, he initially worried BB Lounge's small scale might limit her. However, through Kongming's planning leading to the record label "Fourth Kingdom", Kobayashi transitioned into a continued support role for Eiko within this new structure. His direct encouragement inspired Eiko to create the song "Hot Chill Hot".

His surname Kobayashi (小林) translates to "small forest", combining the characters for "small" (小) and "forest" (林).