Yamato Naoe serves as the central protagonist. His parents reside overseas; his father left Japan due to societal constraints on openly expressing love, motivating Yamato to pursue becoming Prime Minister to facilitate his father's return, prompting his residence at Shimazu dormitory.

Highly intelligent from childhood, Yamato developed a nihilistic worldview through early exposure to adult philosophy books. He initially displayed condescending attitudes towards peers but gradually adopted a more humble and cheerful demeanor. His strategic mindset emerged early, leading him to form the Kazama Family with friends. Key members include Shouichi Kazama, whom he met at a makeshift castle, Kazuko Okamoto, Gakuto Shimazu after mediating a conflict, and Takuya Morooka. The group later recruited Momoyo Kawakami as protector after losing their secret base to older children. Yamato secured this by promising to become Momoyo's underling, sealing their agreement with a pinkie swear and a rare baseball card.

Yamato deeply values his hermit crabs, Yadon and Karin, a passion shared with his mother. His father once instructed him to kill them to build resilience through loss, but Yamato refused. His father praised this defiance, emphasizing the importance of protecting cherished things. This principle extends to his relationships, particularly within the Kazama Family, whom he considers his only true friends despite maintaining an extensive network of strategic contacts.

A pivotal childhood moment involved the Kazama Family discovering an agave plant. During a storm, they stabilized it with ropes and cloths, assisted by Miyako Shiina. After witnessing its bloom, they transplanted it behind their hideout building, symbolizing their lifelong bond. Yamato later shared a class with Miyako in fifth grade but initially avoided her due to severe bullying she endured. He rationalized this distance by believing bullied individuals were at fault, though he eventually intervened.

Momoyo later confessed her feelings, asking Yamato to follow her forever. He declined, seeking equality rather than subordination. He proposed matching her physical strength with his intellect by aspiring to become Prime Minister. Momoyo accepted these terms, and their relationship remained close yet unconsummated, with her awaiting his fulfillment of this promise. Though aware of Miyako's romantic feelings, Yamato consistently rejects her advances, viewing her only as a friend and feeling unworthy to reciprocate.

As a strategist, Yamato employs cunning tactics to overcome challenges, preferring intellectual solutions over physical confrontation. He demonstrates exceptional deductive reasoning and multitasking abilities, notably leading Class-F to victory against the numerically superior Class-S army, which possessed formidable fighters like Momoyo and intellectual prodigy Touma Aoi. His persuasive skills enabled him to recruit powerful allies such as Kuki Ageha and Otome Kan.

Yamato conceals a collection of pornography at the Kazama hideout with friends Gakuto and Takuya. He exhibits a competitive streak, particularly towards Shouichi, whom he wishes to surpass in displays of masculinity despite Shouichi's lesser intellect. In romantic contexts, he displays a passionate, dominant side, claiming this stems from his equation of love with life itself.

Physically, Yamato stands 170 cm tall with spiky dark brown hair and brown eyes. He presents a calm, composed appearance and wears standard school attire. His personal philosophy emphasizes humility and understanding others to foster smooth relationships.