Saitama appears as a 25-year-old bald man of average height, possessing a lean athletic build. His defining feature is a completely hairless head, a direct result of an intensive three-year training regime. His visual portrayal shifts between simplistic cartoonish styles in casual moments and sharply detailed renderings during serious confrontations. He typically dons a yellow jumpsuit, white cape, red gloves, and red boots for hero work, while his casual wardrobe includes shirts and hoodies with humorous designs like "Oppai" (Boobies) and "Ke" (Hair). Before his hero life, Saitama was a disillusioned unemployed salaryman. His path changed when he impulsively rescued a cleft-chinned child from the monster Crablante, using his own necktie as a weapon. This event ignited his commitment to heroism, leading him to adopt a brutal daily routine: 100 push-ups, 100 sit-ups, 100 squats, and a 10km run, supplemented by a banana-only breakfast and enduring extreme temperatures without climate control to build mental fortitude. The training caused severe physical distress, including vomiting blood and intense muscle pain, yet he persevered. Significant hair loss began around 18 months, culminating in complete baldness after three years. This training unlocked immeasurable physical power: strength capable of planetary destruction, speed enabling interstellar travel like leaping from the moon back to Earth, nigh-invulnerability allowing him to withstand cosmic-level assaults such as Gamma Ray Bursts, and sensory abilities including survival in space and long-distance vision. Paradoxically, he struggles with mundane tasks like killing mosquitoes. This overwhelming power triggered an existential crisis, numbing his emotions and fostering perpetual boredom due to the lack of challenging opponents. He often permits enemies to power up fully before defeating them anticlimactically with a single punch. Despite his apparent indifference, Saitama displays complex moral integrity. He anonymously protects civilians and deliberately avoids taking credit for heroic acts to preserve other heroes' reputations, exemplified when he absorbed public criticism himself after the Deep Sea King incident. He exhibits genuine concern for practical matters like supermarket sales, property damage to his apartment, and basic bodily needs, such as breaching a shelter wall during a monster attack solely to find a restroom. His memory for names and faces is notably poor, though he demonstrates tactical awareness and perceptiveness in analyzing situations and character motives. Following the destruction of his Z-City apartment during the Monster Association arc, he relocated to the Hero Association Headquarters in A-City. Registered as "Caped Baldy" (A-Class Rank 39), he mentors the cyborg Genos and forms alliances with heroes like Mumen Rider and Bang. Battles against Boros and Cosmic Fear Mode Garou pushed him to employ "Serious" techniques, revealing his limitless power growth during combat. Against Garou, he accidentally destroyed half of Jupiter's gaseous atmosphere with a "Serious Sneeze" and later inadvertently learned time travel to prevent global catastrophe, though he retained no memory of the alternate timeline.