Dang, puberty hit Charlie Brown like a bus!
Saitama is a guy who's a hero for fun. After saving a child from certain death, he decided to become a hero and trained hard for three years. Though he's now so strong he can defeat any opponent with a single punch, lately he feels as if, in exchange for overwhelming power, he's lost something even more important.
Most stories involve their hero getting stronger and better over time. One Punch Man's creator, who goes by the name ONE, opted for something different, giving us a hero who (as the name implies) could already defeat any enemy with a single blow. Any foe, any strength, any powers, one punch. While out hunting for a job one day, Saitama met a monster who was looking for revenge on a child who'd pranked him; unwilling to let the kid die, Saitama remembered how he'd wanted to be a hero when he was young, not a salaryman, and so set his life on a new path. A path of punching.
One Punch Man was created as a web comic,
basically just meant to be a one-off gag that would help creator ONE learn to use his new manga software. The art was rough and simplistic, which is why his costume is just a yellow jumper with boots, gloves, and a cape. He doesn't even have trunks like Superman, just a belt with a disc buckle. Eventually he got a little zipper at his neck, but the costume remains pretty simple. The sculpt is as detailed as it needs to be, putting small wrinkles near the joints and the impression of muscles beneath the cloth. His cape clasps at the collarbones, and is molded to shape itself around the rear of his body, pressing against the small of his back and around his legs.
Despite itself, the comic became wildly popular, even attracting fans among famous, popular manga artists. One such artist, Murata Yusuke, was such a fan that he contacted ONE about collaborating on a "remastered" version of One Punch Man. The art became much much more detailed, but still retains the simple roots, like Saitama's bald, egg-like head.
Sometimes Saitama will get serious in battle, at which point his art style shifts: rather than the large, cartoony eyes, he suddenly looks more like a "normal" anime/manga character, with a pointier chin and more humanoid eyes. McToys included an alternate head so you can choose whether you want your figure to look goofy or serious.
The only other pack-ins are a pair of alternate hands:
fists, because he's not called One Slap Man. All four of the hands seem slightly too small for the body. He's done in a 7" scale (coming in just a little below 7¼" tall), but the hands look like they would be undersized on a Marvel Legend.
That's not even the only anatomical oddity, either.
Saitama is like McFarlane's Fortnite figures, in that it has good articulation. There are hinged toes, Revoltech-style ankles and wrists, double-hinged knees and elbows, swivel thighs hidden by the shape of the sculpt, swivel/hinge hips, a balljointed chest, swivel biceps, swivel/hinge and balljointed shoulders, and balljoints at the top and bottom of the neck. It's mostly good, though the upper legs don't really allow the hips to move to their fullest potential. What's strange, though, is that the knees seem to have been sculpted too low on the leg. Like, the upper half of the joint is where the lower should be. It may jut be an optical illusion caused by the design of the hips, but it looks weird; they should have accommodated for it.
McFarlane's website claims this figure "features accurate and hyper realistic paint decorations," which is just comical: he wears bright red and yellow, nothing with patterns or even complicated shading. Everything might as well have been molded in color. The faces are painted well enough, but "hyper realistic" is a joke. The figure includes a flat black disc base with white outlined letters tampographed on top. That's done well enough, for what it's worth.
There are both Figma and SH Figuarts versions of Saitama available, but honestly, this one has the best sculpt of the three. Plus, it's far more affordable. There are a couple problems (the hands, the knees) and no accessories, and his scale means he won't fit in with most other superhero toys you have, but it's nice to have a One Punch Man at retail.