Jūgo Yama is the male protagonist of the anime Nanana's Buried Treasure. He is a second-year high school student of average height with brown hair and purple-blue eyes. Frequently seen in his school uniform with a red undershirt, he also favors casual attire like shorts and open button-up vests. His daily training regimen keeps him physically robust and ready for combat.

Jūgo's personality is defined by a desire for a normal, quiet life, a goal constantly undermined by his circumstances and his own nature. He is generally level-headed and cool under pressure but possesses a competitive streak that leads him into arguments and physical fights with those he disagrees with. A self-proclaimed enthusiast for maids, he has a notable perverted side, demonstrated by his willingness to risk injury to fondle his ghost roommate or his attempts to peep on girls at a hot spring.

His background reveals that he is the son of the leader of Matsuri, a secretive syndicate of thieves. However, after speaking out against his father's ideology, Jūgo was disowned and exiled to the artificial island of Nanaejima to finish his schooling. Despite his rejection of the family business, his upbringing has left him with exceptional thieving skills, including high-level combat techniques, acrobatics, and the ability to fall without hurting himself. He keeps up with his training daily to maintain these abilities.

The core of Jūgo's motivation shifts after moving into Room 202 of the Happy House, a low-rent apartment he chooses out of financial necessity. There, he discovers his new home is haunted by the ghost of Nanana Ryūgajō, a girl who was murdered in the room a decade prior. Bound to the apartment, Nanana spends her time playing video games and consuming pudding. Though initially reluctant, Jūgo warms to his roommate and makes a solemn vow to find her killer, hoping to allow her spirit to pass on. This promise drives his central role in the story, pulling him into the dangerous hunt for the Nanana Collection, a set of legendary treasures with supernatural powers, which he believes will provide clues to the murder.

In pursuit of this goal, Jūgo joins his school's Adventure Club. His relationships are central to the narrative. His bond with Nanana is built on immense mutual trust, characterized by playful physical and video game fights (which she always wins) and his near-instinctive routine of buying her pudding. His determination to fulfill her wishes, even when conflicted about whether he wants her to leave, is a constant source of character development. With the brilliant but eccentric detective Tensai Ikkyū, Jūgo shares a competitive rivalry that carries undercurrents of romantic interest and deep respect for her abilities, even when he finds her annoying. He also maintains a connection to his past through Yukihime Fugi, who is both his martial arts teacher and a childhood friend he considers like an older sister and his first love.

Throughout the series, Jūgo is forced to confront his own resolve. He questions whether he truly wants Nanana to find peace and move on now that they have grown so close. He also struggles with a deep-seated distrust of others, a trait even his father notes, yet he consistently chooses to act with integrity and loyalty, particularly toward Nanana and his friends in the Adventure Club. While he claims to act for purely personal motives, he repeatedly risks his life to protect others and demonstrates a proficiency for treasure hunting and evasion that surpasses even trained members of Matsuri. His practical skills, combined with his developing sense of purpose, make him a formidable treasure hunter despite his ordinary aspirations.