Hiroomi Souma is the assistant chef at the Wagnaria family restaurant. He is twenty years old and has short, dark blue hair and dark blue eyes. His expression is most often a serene, closed-eye smile, a feature he shares in common with some of his colleagues but which belies his true nature.

Beneath this placid exterior, Souma is a shrewd and calculating individual. His primary method of navigating his work life is through the collection and strategic use of other people’s personal secrets. He is portrayed as a master of information gathering, able to unearth a person's deep, embarrassing secrets within a single day of meeting them. He employs tactics such as tricky wordplay, digging through personal belongings like trash, and focused observation to acquire this leverage. Once he possesses a secret, he uses it to threaten his coworkers into doing his share of the work, cheerfully reminding them of their vulnerability whenever they try to hold him accountable. For example, he discovered an old photograph of his colleague Souta Takanashi dressed in girls' clothing and uses it as a constant threat.

Souma’s motivations are complex. On the surface, his actions are driven by laziness, as he consistently avoids his culinary duties and prefers to have others complete his tasks for him. However, his interest in the personal lives of those around him runs deeper than simple manipulation. He finds genuine excitement in discovering and sometimes revealing secrets, treating the ensuing reactions as a form of entertainment in an otherwise mundane workplace. While he seems to enjoy the power this knowledge gives him, his meddling is rarely outright malicious. He often acts as a chaotic agent, stirring up situations for his own amusement or to provoke specific outcomes, such as trying to advance the romantic interests of his fellow cook, Jun Satou.

In his role at Wagnaria, Souma is technically a co-chef, but his aversion to work means he is considered only an assistant chef. His role in the story is that of an information broker and a comedic instigator. He is rarely seen performing his kitchen duties, as he is too busy observing, collecting secrets, and pestering his coworkers. Despite his manipulative habits, he is a permanent and essential part of the restaurant's dysfunctional dynamic.

Souma’s relationships with his coworkers are largely defined by the secrets he holds over them. He holds leverage over characters like Souta Takanashi, the small and young-looking Popura Taneshima (whose attempts to grow taller are a secret he knows), and the katana-wielding Yachiyo Todoroki (whose violent history of attacking men he has witnessed). A notable exception is his relationship with Mahiru Inami, who has severe androphobia. Souma is genuinely terrified of her violent, punching response to men, and he goes to great lengths to avoid physical proximity. His solution is to communicate with her via cell phone, even from just around a corner. He also has a unique bond with Jun Satou, the head chef. Although Satou frequently beats Souma with a frying pan for his incessant and failed meddling in his love life, their interactions suggest a deep-seated, trusted friendship. Souma understands the boundaries not to cross, such as never telling Yachiyo directly about Satou's feelings.

One of the most significant relationships involves Aoi Yamada, a new hire who inadvertently discovers Souma’s greatest weakness: the fact that no one knows any secrets about his personal life. By simply crying over this fact, Yamada flusters him completely, exposing a rare moment of vulnerability. Although this incident leads to a misunderstanding that makes Taneshima view him as a heartless bully, Yamada later grows deeply attached to him, calling him onii-chan (big brother) and considering him part of her perfect family, much to his visible chagrin.

Souma demonstrates very little character development in terms of changing his core manipulative nature. He remains a lazy and calculating schemer throughout the series. The most notable development in his personal life is his begrudging tolerance of Yamada’s affection, which reveals a crack in his otherwise impenetrable, secretive armor and forces a new, unwanted dynamic upon him. His abilities lie not in physical strength or culinary skill, but in psychological manipulation, deductive reasoning, and information gathering. His talent for uncovering secrets is almost supernatural, and he uses this power with surgical precision to control his environment and ensure he does as little work as possible.