John S. is a young man of average height and build, characterized by his short blonde hair and blue eyes. He is most often seen wearing a flat cap atop his head, paired with a white shirt, blue overalls secured with a black belt, and dark boots. At twenty-one years old, his simple, rural appearance stands in contrast to some of the more flamboyant members of his organization.

His personality is generally relaxed and easygoing, often displaying a casual and cunning nature. He claims to hate chores but is not a lazy person, proving himself fully capable of carrying out the missions assigned to him. While he can be polite and seemingly kind, he shows no regard for his enemies and feels no guilt in dealing with them brutally when the situation requires it. This unwavering determination in combat is sometimes paired with a degree of overconfidence in his own abilities, which can become a weakness.

The core motivation for all of his actions is his family. Prior to joining the Guild, John was a poor farmer in North America, and he took on his dangerous role specifically to provide for his large family. His love for them, particularly his younger sister whom he cherishes and constantly spoils, is the driving force behind his willingness to perform any task, no matter how dirty it may be. His personal values are rooted in his humble origins, leading him to deeply hate loneliness, poverty, and people who prioritize money above all else.

John S. is a member of the Guild and plays the role of a supporting antagonist. He often works in a close partnership with his eccentric colleague, Lovecraft, acting as a field operative. He first appears in the middle of a conflict between the Armed Detective Agency and the Port Mafia, warning them of the Guild's arrival. Later, he and Lovecraft ambush agency clerks in the countryside. Although he nearly captures them using his ability, he is ultimately defeated and arrested. He is later released, presumably due to the Guild's influence.

His role becomes more sinister during the Guild's emergency plan to cause mass destruction in Yokohama. John is tasked with using his ability on a captive Q, connecting his grapevines to all the trees in the city. This allowed any harm inflicted on the city's flora to be transmitted to Q, activating Q's own dangerous curse ability on the perpetrator. This plan is thwarted by the combined efforts of Osamu Dazai and Chūya Nakahara.

His key relationship is with his partner, Lovecraft, whom he considers one of his few friends. In contrast, his relationship with the Guild's leader, Francis Fitzgerald, is fraught with animosity. Although he works for Fitzgerald, John hates the man's endless ambition and arrogance, viewing him as a manipulative capitalist. After the Guild's defeat and Fitzgerald's disappearance, John demonstrates development by choosing not to abandon the organization. Instead, he stays to pacify an internal rebellion and becomes the interim leader of the Guild remnants. When Fitzgerald later re-emerges, an infuriated John swears to crush his former leader's ambitions, marking his evolution from a hired operative to an independent actor driven by his own convictions.

John S. possesses an ability named The Grapes of Wrath. This power allows him to grow powerful grapevines from his own body, typically from his neck. He uses a tool like a navaja to injure himself and plant seeds, causing the vines to erupt. By grafting these vines to other plants, he can turn all the flora in the surrounding area into an extension of his own body. This allows him to capture or hold people and objects with tremendous strength, shield himself from attacks, and sense vibrations through the ground, making him difficult to ambush. He can also use the network of vines to share senses or transmit pain to another person, a technique he used to devastating effect in combination with Q's ability.