Musashi, alias Jessie, serves as a core member of Team Rocket alongside Kojiro (James) and Nyasu (Meowth). Her difficult childhood involved poverty and instability after her mother Miyamoto, a high-ranking Team Rocket agent, vanished during a mission to record Mew's voice in the Andes when Musashi was about five. This led Musashi to enter a financially strained foster home where food scarcity sometimes forced reliance on snow-based meals. Before joining Team Rocket, Musashi cycled through multiple unsuccessful careers. She enrolled in a Pokémon nursing school intended for Chansey but failed to graduate due to physiological incompatibilities, like being unable to use Sing. A meaningful parting gift from a Chansey friend—half an egg-shaped pendant—became a keepsake. She later attended the Pokémon Trainers' school Pokémon Tech alongside Kojiro, where both achieved the institution's lowest-ever scores. Subsequently, they joined a Sunnytown bicycle gang; Musashi earned nicknames like "Big Jess" and "Chainer Jessie" for swinging a chain while riding. Other pre-Team Rocket endeavors included fleeting romantic relationships that often ended poorly, a stint as a TV weather reporter, and brief work as a ninja. She also obtained a Contest Pass in Hoenn during this time, its initial expiration hinting at earlier, unelaborated connections to the region. The specifics of her recruitment into Team Rocket remain unclear, though she joined separately from Kojiro and initially clashed with him and Nyasu before forming their enduring trio. During the Diamond & Pearl series, Musashi pursued Pokémon Contests across Sinnoh under the alias Jessilina, aiming to become a Top Coordinator. She secured three Ribbons using Dustox, Yanmega, and Seviper, obtaining additional Ribbons through Kojiro’s substitute victory and a gift from Princess Salvia. This qualified her for the Sinnoh Grand Festival, where she reached the semi-finals but lost to Hikari (Dawn). The defeat devastated Musashi; she discarded her Jessilina costume and temporarily abandoned Contests after Hikari later lost in the finals. She warned Hikari to eventually become Top Coordinator, indicating latent support despite their adversarial dynamic. Her Pokémon team included Wobbuffet (accidentally acquired via trade), Seviper (caught after it ate her riceball), Yanmega (evolved from Yanma), and Dustox (evolved from Wurmple). She released Dustox to allow it to breed with a shiny male Dustox. Musashi’s relationship with Kojiro features deep mutual reliance. They consistently support each other through failures and dangers, displaying protective behaviors and emotional vulnerability. This includes refusing abandonment in crises, sharing personal insecurities, and collaborative efforts like Kojiro selling collectibles to fund her Contest attire. Their bond involves physical closeness like shared sleeping arrangements and embraces during distress or joy. Despite her antagonistic role, Musashi displays occasional compassion, notably toward her Pokémon and Kojiro. Her loyalty to Team Rocket persists despite Giovanni’s frequent dismissiveness toward her team’s failures.