Kunikida attends North High as Kyon's classmate in Class 1-5, alongside Taniguchi. He shares a junior high background with Kyon, Sasaki, Sudou, and Okamoto at an unnamed institution. During those earlier years, he cultivated a taste for Western music, even requesting its playback in the school cafeteria during lunch. His enrollment at North High was motivated by an interest in fellow student Tsuruya.

Quiet and reserved, Kunikida forms a contrast to the voluble Taniguchi, typically allowing his friend to dominate their exchanges. Academically, he stands out as a diligent high-achiever, capable of breaking down complex subjects for peers such as Taniguchi. He harbors a competitive streak regarding academic performance, notably concerning himself with Sasaki's university entrance exam results despite being only a first-year high school student.

Having known Kyon since junior high, Kunikida observes Kyon's interactions and concludes that Kyon has a preference for "weird girls," citing his associations with the unconventional Sasaki and Haruhi Suzumiya. This observation leads Kunikida to interpret it as evidence of Kyon's romantic interest in Haruhi.

Kunikida often finds himself an unwilling participant in SOS Brigade activities. He serves as a "guinea pig" during their baseball game and appears in their amateur film, *The Adventures of Mikuru Asahina Episode 00*.

Despite remaining unaware of the SOS Brigade members' true supernatural natures, Kunikida possesses enough perception to sense something unusual about them. He specifically reports feeling "inhuman vibes" from Yuki Nagato and Mikuru Asahina, making him one of the rare ordinary humans aware that the brigade members are not normal.