Jeremy Tsurgi, known as Zenjirou Tsurugi in the original Japanese version, is a central character who lives several towns away from the protagonist, Mikey Kudo. His background is deeply rooted in the practice of kendo, a martial art that has instilled in him a strong sense of principled behavior and a deep-seated hatred for immorality and injustice. This discipline is a core part of his identity, shaping his initial interactions with Mikey, whom he first encountered at a kendo tournament between their schools.

His defining personal motivation is his self-proclaimed status as "Mikey's eternal rival". This rivalry stems from a tournament where Mikey, who had no formal kendo training, managed to defeat him. This loss greatly affected Jeremy, fueling a persistent, if slightly one-sided, competitive drive. Despite his bluster about being a rival, Jeremy’s personality is initially marked by significant cowardice. He is often terrified by the dangers of the Digital World, frequently clinging to Mikey's arm in fear and showing a pronounced phobia of heights. To mask his anxiety or process the surreal situations, he often makes jokes and references to video games and pop culture, particularly in the English version of the anime. Adding another layer to his character, Jeremy has a severe and open crush on a fellow general named Nene Amano, a fascination that often leads him to act foolishly or competitively, even going so far as to trample over Mikey for a chance to be closer to her.

As a human from the real world, Jeremy’s role in the story begins when he is unexpectedly transported to the Digital World alongside Mikey and their friend Angie Hinomoto. While not the primary general like Mikey, Jeremy proves to be a valuable and capable member of the Fusion Fighters. When Mikey is incapacitated, Jeremy steps up to become a capable leader, taking command of their Digimon forces and strategizing in battle. His key relationships evolve significantly over time. His bond with Mikey deepens from a simple rivalry into a profound mutual respect and friendship, and Mikey later acknowledges him as a great warrior who was always there for the team. He shares a frequent dynamic with Angie, often agreeing with her exasperated reactions to Mikey's rash decisions. He also develops a special bond with the red Pickmon, a small, star-shaped Digimon, and often fights using the Rare Star Sword, a weapon formed from his partner and the other Pickmonz.

Jeremy’s character development is defined by his journey from cowardice to courage. His growth is first notably demonstrated in an early battle when, despite his fear of heights, he hurls the Rare Star Sword from a great height to strike an enemy Digimon and save the Village of Smiles. This act proves that his principles can overcome his fears. During the first major story arc, he is sent back to the human world but his unwavering friendship and courage, combined with Angie's, provide the emotional catalyst that allows their Digimon partner Shoutmon to digivolve into a more powerful form to defeat a major enemy. His commitment to his friends is shown when he returns to the Digital World in the second season, demanding a Fusion Loader so he can actively fight alongside his "eternal rival" once more.

In terms of abilities, Jeremy is a skilled kendo practitioner, giving him a natural aptitude for swordplay. This skill translates directly to the Digital World, where his primary ability is wielding the Rare Star Sword in battle. After returning to the Digital World in the second season, he is granted his own Fusion Loader and receives a portion of Mikey's Digimon collection, including powerful partners like Ballistamon and Deputymon, allowing him to perform DigiFusions and fight as a fully-fledged general in his own right.