Masahito Date is a middle-aged man, approximately forty years old, who appears as a supporting character in the survival story. He is of average height and weight, with a build that is slightly athletic enough to endure the harsh jungle environment. His face is long, framed by short black hair and a small, trimmed beard, and he wears classic round glasses that contribute to a professional appearance.

Before being thrust into the deadly island game, Date worked as a competent doctor at the same hospital as a nurse named Shiki Murasaki. During his time there, he became involved in a medical malpractice incident. When he realized that Murasaki, out of respect for him, was willing to help cover up the mistake, he manipulated the hospital management into placing the blame entirely on her, sacrificing her career to protect his own. In retaliation, Murasaki entered his name as a participant in the real-life version of the Btooom! game, a violent competition in which players use explosive devices called BIMs to eliminate each other on a remote island.

Date's personality is defined by self‑interest, manipulation, and a cold, calculating nature. He is a man who prioritizes his own survival above all else and is willing to betray anyone to achieve his goals. On the island, he is a two‑time participant, meaning he has already played at least one prior round, which gives him experience and familiarity with the game's mechanics. He uses his professional credibility and outwardly trustworthy demeanor to infiltrate alliances, only to discard his teammates the moment it benefits him. His primary motivation is to escape the island alive, and he will stop at nothing to secure the necessary resources, including other players' BIM chips.

His key relationships are largely adversarial and transactional. The most significant is with Shiki Murasaki, whose betrayal led to his presence on the island, though they do not interact directly during the story. Among the other players, he forms temporary ties solely for exploitation. He is known for his strategic thinking and ability to assess danger quickly, but his physical capabilities are unremarkable; he relies on cunning and experience rather than raw combat skill. In the end, Date's arc concludes with his death while attempting to flee the island. He is shot in the face by another player who wants the gas mask he is wearing, and the mask itself is rendered useless in the process. His development is minimal, as he remains consistently self‑serving and meets his end without redemption or change. His notable abilities include his medical knowledge, though this is not prominently used on the island, and his honed survival instincts from his previous exposure to the game.