Yūsuke Fujisaki, known by his nickname Bossun, is characterized by his idealism, enthusiasm, and strong desire to help others. As the leader of the Sket Dan, he is deeply committed to solving people’s problems, no matter how trivial they may seem. His determination often leads him to go to great lengths for others—even tracking down something as insignificant as a lost candy wrapper if it holds emotional value to the person involved.

Despite his earnest nature, Bossun is socially awkward and somewhat childish. He struggles with basic social cues, especially around girls or when being filmed, and becomes easily flustered, embarrassed, or dejected when criticized or excluded. When idle, he often indulges in playful or immature behavior such as reading manga, joking around, or playing with small toys, showing his lighthearted and carefree side.

In strange or exaggerated situations, Bossun frequently assumes the role of the straight man, usually alongside Himeko, and may initially reject requests he deems absurd though he almost always accepts them in the end. Beneath his comedic and awkward demeanor, Bossun possesses a sharp intellect and strong analytical ability. He demonstrates exceptional problem-solving skills, creativity, and logical reasoning, traits that have earned him the respect of his peers. While others view him as a genius in both artistic and deductive thinking, Bossun remains humble and dismissive of his own talents, focusing instead on using them to help others.

Bossun is a teenage boy with messy dark hair that curls upward above his ears, giving him a distinctive silhouette. He is almost always seen wearing his trademark red horned Poppman cap and a pair of goggles resting on his head. His usual outfit consists of a white short-sleeved overshirt rolled up at the sleeves, worn over a blue-and-white shirt of his own design bearing the word “SKET” across the chest. He typically pairs this with blue knee-length shorts, black ankle bands, and sandals.

He also wears wristbands on both wrists, one featuring red, white, and blue stripes, and the other bearing the Sket Dan emblem on a black band. Several decorative pin buttons are attached to his shirt, adding to his casual and individualistic look. Bossun is known for his highly expressive face, often exaggerated for comedic effect; one of his most notable expressions is his “embarrassed” face, in which he puckers his lips in a comically awkward manner.

On his fifteenth birthday, Yūsuke Fujisaki learned that he was not biologically related to his mother, Akane, or his younger sister, Rumi. He discovered that his real parents were Akane’s close friends, Haru and Ryōsuke Fujisaki, who both died in separate car-related accidents on the day he was born. Haru passed away shortly after giving birth to Yūsuke and his twin brother, Sasuke, while Ryōsuke died after saving a child from an oncoming vehicle.

Shaken by the revelation and struggling to process his identity, Yūsuke ran away from home, wandering aimlessly in emotional turmoil. During his time away, he met Taisuke, the boy his father had saved years earlier. Taisuke gave Yūsuke a letter written by Ryōsuke, originally intended for Haru and their newborn children. The letter expressed Ryōsuke’s wish that his children grow up to help others and bring kindness to those in need.

Initially angered by his father’s selflessness, believing it had cost his life, Yūsuke rejected the message and declared he would live only for himself. However, when he later witnessed upperclassmen bullying another student who would later be revealed as Tsubaki he instinctively intervened despite being outnumbered, realizing he had inherited his parents’ compassion. This event marked a turning point in his life. Having come to terms with his past, Yūsuke returned home to Akane and Rumi, accepting them as his true family and reaffirming his resolve to help others, a principle that would later guide the founding of the Sket Dan.

Concentration Mode
Bossun possesses a unique ability he calls Concentration Mode, which allows him to achieve an extraordinary level of focus and perception. By putting on his goggles and recalling all relevant information about a problem, he heightens his awareness to near-superhuman precision. In this state, he can detect subtle details, such as faint background noises during a phone call, and quickly formulate logical solutions. His concentration also grants him exceptional accuracy with his pachinko-ball slingshot, his primary weapon. However, this state is mentally taxing, and after prolonged use, Bossun is often seen gasping for air as if resurfacing from deep water.

Artistic Talent
Bossun demonstrates exceptional skill in both two- and three-dimensional art. He is adept at drawing, origami, and sculpting small figurines, often surprising others with the quality of his work. His peers in the Sket Dan humorously note that such artistic ability is unusual for a shōnen manga protagonist, yet it often proves useful in solving problems or entertaining clients.

Vocal and Facial Impressions
Bossun has a natural gift for mimicry, able to reproduce the voices and expressions of various people with remarkable accuracy. His impressions include well-known Japanese figures such as comedian Rakutarō Sanyūtei and baseball player Eiji Bandō, a skill he often uses for comic relief or to lighten tense situations.

Himeko (Hime Onizuka)
Bossun’s relationship with Himeko is complex neither romantic nor purely platonic. The two share a close bond marked by mutual trust, banter, and unspoken affection. In the School Trip Rhapsody arc, Bossun admits he has never seriously considered his feelings for Himeko “until now,” suggesting growing awareness of his emotions. He becomes visibly irritated upon suspecting that Himeko is dating Katō, mirroring his father Ryōsuke’s dynamic with Haru, whom he affectionately referred to as “just a friend.” During the Trouble Travel arc, Bossun loses his composure whenever Himeko is in danger, acting impulsively to protect her. Switch describes them as an inseparable boke and tsukkomi duo, emphasizing their perfect comedic and emotional balance within the Sket Dan.

Roman Saotome
Roman develops an immediate infatuation with Bossun due to her “Otome Filter,” which causes her to interpret ordinary gestures as romantic acts. After Bossun rescues her from an oncoming truck, she begins referring to him as “my prince.” Though her affection for him is exaggerated and largely one-sided, Bossun treats her kindly and regards her eccentricity with good-natured patience.

Saaya Agata
Initially, Saaya frequently insults and mocks Bossun, unable to communicate comfortably with boys because of her tsundere personality. Bossun helps her confront and manage this behavior, leading her to gradually develop genuine romantic feelings for him. Despite her eventual confession, Bossun views Saaya only as a friend and remains largely unaware of her affections until Himeko confronts him about it during the School Trip Rhapsody arc.

Sasuke Tsubaki
Bossun and Tsubaki share a rivalry that often leads to arguments and competitive exchanges, though beneath their friction lies mutual respect. After discovering that they are twin brothers, their relationship evolves into a more supportive one, with both occasionally seeking advice or assistance from the other. They still maintain their combative rapport, but moments of camaraderie reveal their underlying familial connection and how alike they truly are.