Normally, Sakamoto appears to be just a regular (if a bit fat) man with gray hair tied into a ponytail and a small, gray mustache, often seen wearing round glasses and a green apron over his normal clothes.
However, through unknown means, Sakamoto is capable of transforming into a much taller and leaner form whenever he gets serious.
Whilst in this form, Sakamoto's facial features become far more well-defined and he loses his mustache, Shin himself even noting that he looks a lot more handsome overall.
Sakamoto isn't much of a talker and instead prefers to let his actions speak for themselves. He deeply loves his family, shown by the fact that he left his hitman profession just to be with them, and is very protective of them. He also has a great amount of respect for his wife, Aoi Sakamoto.
Sakamoto was once considered to be the greatest assassin to ever live, a man who struck fear into the hearts of bad guys and that was revered by fellow hitmen the world over.
However, one day Sakamoto met and fell in love with a beautiful clerk by the name of Aoi, he became so smitten with her that he decided to leave behind the world of hitmen so that he could be with her.
After dating for a while, Sakamoto and Aoi would get married and open up their own little convenience store, eventually having a daughter named Hana.
Over the years, Sakamoto would fall out of shape and become fat.
Aoi Sakamoto: Sakamoto's wife and the main reason he left the hitman business, he deeply loves and respects her, trying his best to protect her but also to keep from making her angry. A good example of this can be seen in how he tries to keep in line with her rules to avoid her divorcing him.
Hana Sakamoto: Sakamoto's daughter and only child. Although they do not interact much, Sakamoto deeply loves her and will do his best to protect her.
Shin: Sakamoto's former partner from his glory days who now works as an employee at his store. Sakamoto cares about Shin, evident by the fact he saved him from being killed, often confiding in him and trusting him above all else. Shin is the closest thing Sakamoto has to a friend. Shin harbors a great deal of respect and admiration for Sakamoto, seeing him as a mentor and
Lu Xiaotang: A young woman from a Triad family whom Sakamoto saves for the sole purpose of making pork buns for him. Ever since then, she has come to work in his store although she seems to have friction with Shin. Sakamoto seems to have a great deal of appreciation and concern for Lu comparable to that of Shin, demonstrated by his constant urge to protect her. He goes through great lengths to let Lu stay as a member of his store and his family when Wutang comes looking for her.
Nagumo: An old friend of Sakamoto's as well as a member of The Order, an elite assassin group that Sakamoto was formerly a member of. It appears that they first met and became friends during the time they spent in their shared JAA class. At one point in Chapter 45, Nagumo defends Sakamoto's store while he is away, showing he is willing to do favors for Sakamoto, as well as demonstrating that Sakamoto trusts Nagumo enough to protect his family and his store.
Overall Capabilities: As the legendary hitman, Sakamoto was renowned throughout the underworld for his ability to kill his targets and is known for his expertise in both hand-to-hand combat and mastery of different weapons. Even in his chubby form, Sakamoto is a force to be reckoned with.
Enhanced Strength: Sakamoto boasts incredible physical might, being capable of easily decapitating people and kicking Shin (who is a very capable fighter in his own right) across his entire store. A testament to his extreme strength was when he stabilized a collapsing section of the Tokyo Tower (likely weighing hundreds of tons) by pulling it from the other side with a steel cable. He's also been shown performing other feats of strength, such as stopping a fast moving bus with nothing but a traffic sign, holding a person aloft with one hand and being able to destroy Son-Hee's chakram with just a frying pan. Sakamoto's strength makes him highly effective at using improvised weapons, such as throwing chopsticks with enough force to pin people to walls and slamming a person around using the suction of a vacuum cleaner.
Enhanced Durability: Sakamoto has phenomenal durability being able to withstand a kick from Bacho, which sent him flying into an adjacent building with enough force to leave a crater. Sakamoto has also survived extremely tall falls unharmed, withstood numerous point-blank explosions from Boiled and casually handle a day at a bathhouse so intense it left Shin unable to move.
Enhanced Speed & Reflexes: Sakamoto is amazingly quick, being able to dodge Son-Hee and Bacho's "Tofu Scramble Attack" and hit the latter before he could react, dismantle and slice apart multiple opponents' guns in the blink of an eye before incapacitating them, and being able to catch up with a speeding bus on foot. He was fast enough to swat aside sniper rounds fired by Heisuke, though this did injure his hand. Sakamoto is able to briefly run on the side of walls, scoop boiling water out of the air with an instant ramen cup and spin clothing hangers fast enough to deflect bullets.
During his infiltration of the JAA's academies, Sakamoto was able to assemble a gun and fire 67 shots within a minute, all of which were bullseyes. According to the leaderboard, a student Sakamoto managed to fire 89 shots, implying he was even faster in the past.
Enhanced Agility: Sakamoto, despite his size, is actually quite agile which he demonstrated in his fight with Shin when he managed to move around his store quickly enough the younger man couldn't keep up with him or even follow his movements. Sakamoto moves so fast most opponents cannot see him, much less react before he attacks.
Skinny/Prime Form: Although it's unknown how he does it, Sakamoto can assume a form similar to what he had when he was still in shape, gaining a massive boost to all of his physical abilities as demonstrated when he completely overwhelmed Boiled, an extremely capable hitman who'd previously been giving him quite a bit of trouble.
Master Combatant: Sakamoto has incredible skills in both armed and unarmed combat, being more than capable of effortlessly defeating several gun-wielding thugs using nothing but some knives and his own two fists. One of his most notable abilities upon entering civilian life is his ability to use random objects as extremely effective weaponry. Sakamoto has used cooking pots, frying pans, freezers, traffic signs, cough drops, stickers, vacuum cleaners, clipboards, drawers and even pens to brutalize opponents.