Yūichi Jin is known for his laid-back and easygoing attitude, often maintaining a calm and cheerful disposition even in tense or controversial situations such as when he is criticized for protecting a humanoid Neighbor. He is frequently seen carrying a bag of rice crackers, his favorite snack, which he generously offers to others, including former adversaries. Despite the loss of his mother to a Neighbor attack, Jin does not harbor resentment toward their kind. Instead, he advocates for peaceful coexistence between humans and Neighbors, believing that understanding and cooperation are possible between both worlds.

Beneath his carefree exterior, Jin is highly intelligent, perceptive, and calculating. He demonstrates a strong sense of loyalty and responsibility toward his friends and comrades, often taking bold or unconventional actions to protect them. When serious, Jin shows considerable restraint and avoids unnecessary violence, only engaging forcefully when absolutely necessary.

Jin’s true strength lies in his strategic thinking and ability to manipulate situations using his Side Effect, which allows him to foresee multiple future outcomes. This ability makes him one of the most resourceful and influential agents within Border. He effectively uses his foresight to guide decisions, secure allies, and anticipate threats, often orchestrating complex plans for the benefit of others. His friendly personality, high rank, and popularity among Border members give him extensive connections and social leverage tools he readily uses to accomplish critical objectives, such as organizing large-scale operations like the effort to eliminate the swarm of Trion drones causing irregular gates. Jin humorously refers to himself as the “power elite,” though this title appears to be self-ascribed.

Yūichi Jin has medium-length brown hair, neatly combed, and striking blue eyes. One of his signature accessories is a pair of turquoise-tinted sunglasses, which he typically wears around his collar rather than over his eyes.

Jin is most commonly seen in his Border uniform. His outfit consists of a blue jacket with a distinctive black stripe running down the length of each sleeve. The jacket features the Tamakoma Branch emblem on both upper arms. Underneath, he wears a plain white shirt. He completes his uniform with dark brown pants and black boots, maintaining a clean and consistent appearance throughout the series.

Combat Skills
Yūichi Jin is one of Border’s most powerful agents, formerly classified as S-Rank and currently ranked A-Rank. As a member of the Tamakoma Branch, his abilities are formidable enough that he is considered equivalent to an entire squad during defense missions. Jin is capable of taking on multiple Trion Soldiers simultaneously and has held his own against highly skilled combatants such as Hyuse, who wields one of Aftokrator’s Enhanced Triggers.

Jin is exceptionally versatile with different melee Triggers. With Scorpion, he can engage and match opponents like Hyuse in agility and technique. Prior to the introduction of Scorpion, his mastery with Kogetsu placed him just behind Masafumi Tachikawa, Border’s top-ranking solo fighter. After Scorpion’s development, their matches ended in consistent draws, showcasing Jin’s adaptability and continued growth. Even when using a standard blade, Jin has demonstrated the ability to overwhelm multiple elite agents, such as Tachikawa and the entire Kazama Squad, especially when wielding his Black Trigger, Fūjin.

In battle, Jin incorporates hand-to-hand combat into his swordplay, using kicks and tactical movement to disrupt opponents at close range. His foresight also enables him to predict enemy actions in advance, allowing him to evade rather than block attacks and to exploit opponents’ psychological weaknesses, particularly those who are easily provoked. This predictive edge also makes him an exceptionally difficult target for Snipers.

Side Effect: Foresight (未来視, Mirai-Shi, lit. “Future Sight”)
Jin possesses an S-Class Side Effect known as Foresight, which allows him to see potential futures involving any individual he is observing. The length and clarity of these visions depend on the likelihood of the events in question, he can see far into highly probable futures, while improbable ones are shorter and more fragmented.

The nature of his foresight is dynamic: it reveals branching paths, converging timelines, and varying degrees of probability. Jin can track the changing likelihood of outcomes over time and is alerted when the probability of a particular future increases, even if he is no longer observing the individuals involved. This allows him to react to evolving situations with remarkable precision.

However, while his Side Effect is powerful, it is not absolute. Minor changes in circumstance can cause the probability of a previously unlikely event to rise unexpectedly. Likewise, interfering parties who act against Jin’s intended outcomes can shift the flow of events. Nevertheless, by strategically removing obstacles and acting on insight from his visions, Jin is often able to steer events toward favorable resolutions for himself and his allies.

Sōichi Mogami
Although little is known about the specifics of their relationship, Sōichi Mogami served as Jin’s master and predecessor as the wielder of the Black Trigger Fūjin. Jin’s willingness to overcome any opposition in order to inherit Fūjin suggests a deep respect and emotional attachment to Mogami’s legacy.

Takumi Rindō
As the commanding officer of the Tamakoma Branch, Takumi Rindō commands Jin’s respect and loyalty. Jin refers to him affectionately as “Boss,” and the two share a strong understanding rooted in similar philosophies. Rindō often supports Jin’s decisions without needing detailed explanations, as seen during the Black Trigger Capture Arc, where he gave Jin the authority to act on his own judgment, even if it meant defying Border’s upper management.

Osamu Mikumo
Jin sees a kindred spirit in Osamu, particularly in their shared belief that peaceful coexistence with Neighbors is possible. He has protected Osamu on several occasions, even prior to Osamu’s official enrollment in Border, and played a behind-the-scenes role in helping him get enlisted. While Jin often addresses him informally as “Four Eyes,” he clearly values Osamu’s determination and ideals. During the Aftokrator Invasion, Jin used his Side Effect to orchestrate events in Osamu’s favor, though he later blamed himself for Osamu’s injuries and the loss of Replica. Jin has since vowed to support Tamakoma Second as a form of atonement.

Yūma Kuga
Jin views Yūma as a junior he deeply relates to, often seeing his own younger self in him. To ensure Yūma’s acceptance into Border, Jin willingly gave up his Black Trigger, Fūjin, and later claimed he had no ulterior motives beyond wanting to support the next generation and “act cool.” He sincerely wishes for Yūma to enjoy his time in Border and develop freely within it.

Replica
Jin held great respect for Replica, often referring to him as “Sensei” (先生), acknowledging the artificial lifeform’s wealth of knowledge and mentorship. Replica’s capture during the Aftokrator Invasion weighs heavily on Jin’s conscience, and he has promised to make amends by assisting Tamakoma Second in the future.

The given name Yūichi (悠一) is composed of the kanji 悠 (yū), meaning “calm,” “distant,” or “permanence,” and 一 (ichi), meaning “one.” Together, the name may be interpreted as “eternal first” or “serene one,” reflecting Jin’s composed demeanor and dependable presence within Border.

His surname Jin (迅) means “swift” or “fast,” a fitting name given his role as a high-ranking Attacker and his foresight-based Side Effect, which allows him to anticipate and act ahead of others. The meaning aligns well with his quick thinking, agility, and strategic foresight.