A cool, cynical man. He favors witty phrasing and is surprisingly frank with a sense of humor. His sharp sarcasm is biting, and he occasionally drops suave, movie-like lines. He tends to flirt with any woman he meets for the first time, though Otacon notes he's actually quite shy and "all talk." He possesses many traits theoretically unnecessary for a soldier, such as vulnerability and kindness, which he can never fully discard—making him a saint-like hero in a sense. A calm realist, he has a slightly self-punishing streak. However, he fundamentally respects the will of others and shows genuine kindness to those he acknowledges as comrades, often cracking jokes to lighten the mood or put his team at ease.

Solid Snake's partner and irreplaceable best friend, whom Snake evaluates as a "strong man." A genius engineer and elite hacker with a brilliant mind, he primarily supports Snake from the rear. He has a gentle personality, being kind and friendly to everyone. While his cautious nature makes him seem slightly cowardly or wimpy at times, he possesses a level-headedness that prevents him from panicking in most situations. He is poor at physical exercise and dislikes heights (though he later overcomes his acrophobia by learning to pilot helicopters in VR). Despite this, he has a very strong core and an unwavering will to never compromise his beliefs once he has made up his mind. Having endured various tragedies throughout the series, he possesses the mental fortitude to carry out his duties without breaking, earning him high praise and trust from Snake. He feels a deep sense of regret and responsibility for his past mistakes, including the development of Metal Gear, and seeks to atone for them for the rest of his life.

Possesses an androgynous appearance and has been mistaken for a woman in the past. He has a serious and simple-minded personality; Snake once called him "simple, soft, and hard-headed." As a child soldier under Solidus's command, he underwent brainwashing and training, holding a gun for the first time at age six and becoming a platoon leader of the Small Boy Unit at ten. He developed a cruel side, once killing people with a knife as if they were candles on a birthday cake; his masterful yet brutal knife skills earned him the feared nicknames "Jack the Ripper" and "The White Devil." After the civil war, he was taken in by a human rights group and moved to the US, but his mind and body were ravaged by his harsh upbringing and the cruel realities he faced. However, after being counseled by Solid Snake—who once harbored similar internal conflicts—he has gradually begun to reclaim his own reality.