Kawaguchi is a supporting character in the anime Style of Hiroshi Nohara's LUNCH, serving as a junior colleague to the protagonist, Hiroshi Nohara, within their workplace. In the office dynamics, Kawaguchi is positioned as a younger subordinate who looks up to and frequently interacts with Hiroshi, often during the crucial lunch hour.

Personality-wise, Kawaguchi is portrayed as someone who experiences a range of relatable workplace emotions. He is capable of professional success, such as when he closes a major deal, an achievement that makes his senior colleague proud. However, he also shows a more vulnerable side; he can be prone to sulking, as seen when he feels left out after Hiroshi takes a different trainee to an upscale restaurant for a luxurious lunch. As a rookie, he is depicted as having overconfidence, which can sometimes cause mix-ups in a work setting.

Kawaguchi's primary role in the story is to be Hiroshi's work subordinate and a frequent lunch companion. The narrative often focuses on Hiroshi navigating his role as a senior by taking Kawaguchi out to eat. These excursions serve as a backdrop to explore themes of workplace relationships and generational differences. For example, Hiroshi treats Kawaguchi to an affordable seafood bowl to celebrate a professional win, showcasing a senior's benevolence. In another instance, Hiroshi attempts to cheer up a sulking Kawaguchi by offering to treat him to a meal anywhere he likes, which comically ends up at a pancake café primarily frequented by young women. These lunch trips highlight the bond between the two, which is central to Kawaguchi's involvement in the plot. He does not possess any supernatural or special abilities, as his characterization is rooted in the realistic comedy of salaryman life.