Johnny Sasaki was one of the members of Liquid Snake’s army at Shadow Moses, the Genome soldiers, although it’s possible he was couersed into it by Psycho Mantis mind control. His grandfather also guarded the original Snake-the man who became Big Boss-during Operation Snake Eater.During snake’s mission, Johnny suffered from several stomach problems, prompting many trips to the bathroom. He was eventually left to guard the cell of Meryl Silverburgh, who he was infatuated with. His general incompetence and stomach problems allowed both Meryl to escape (in disguise with his clothes, weapons and equipment) and later Solid Snake when he was briefly held prisoner.
He later also showed up as part of the Gurlucovitch mercenaries, but once again allowed another escape due to his issues….Emma Emmerich, the stepsister of Hal “Otacon” Emmerich.
Eventually, Johnny rejoined the US military despite working for the bad guys twice, and was assigned to Meryl’s unit, Rat Patrol I (Which was technically-and unknowingly-serving the real bad guys, the Patriots AI). Although his earlier incompetence was marked by bathroom breaks, now he had at least technology to show what he could do, with a wrist keyboard on his arm that gave stats to his “smart” goggles. He was also an expert in traps. This earned him the nickname “Akiba”, a reference to Tokyo’s electronics district) However, his other character traits still existed, as when he confronted Solid Snake with the safety on his gun still on….and crapped himself during a tense fight with Ocelot’s main unit, the FROGS.
Johnny however was able to redeem himself. Having a phobia of needles, he wasn’t privy to the various nanomachines injections that other soldiers had received, and when Ocelot messed with the system, which affected all soldiers including Snake and Meryl- he wa s able to take Snake to safety. Later, he saved Meryl from drowning, and administered CPR to her. She rewarded her with a kiss.
Later, when the Outer Haven operation was underway, Johnny-although earlier checking out Mei Ling-saved her and Snake from a group of FROGS, and later when Snake left for the Patriots AI, he supported Meryl in combat.
During the battle, Johnny mentioned that the reasons he’d been able to help is that he hadn’t taken any shots, and Meryl reasoned that this is why he might’ve been having stomach aches and accidents all the time, as the nanomachines didn’t seem to suppress them. As they were in combat, he revealed his true feelings for her and wanted to marry her. She refused his proposal, but only because she wanted to do things her way…so she proposed to him.
….and as they tried to work out their wedding plans, they continued to fight the Frogs.
Later, after Snake’s sucess and battle with Liquid Ocelot, the two got married near Snake’s plane, the NOMAD, in a ceremony attended by the other RAT PATROL members (and officiated by Ed, one of the team as well), Meryl’s father Roy Campbell, Huey “Emmerich” Otacon, his adopted daughter Sunny, and Mei Ling.