Putting his life on the line, Willem Kmetsch leaves his loved ones behind and sets out to battle a mysterious monster, and even though he is victorious, he is rendered frozen in ice. It is during his icy slumber that terrifying creatures known as "Beasts" emerge on the Earth's surface and threaten humanity's existence. Willem awakens 500 years later, only to find himself the sole survivor of his race as mankind is wiped out. Together with the other surviving races, Willem takes refuge on the floating islands in the sky, living in fear of the Beasts below. He lives a life of loneliness and only does odd jobs to get by. One day, he is tasked with being a weapon storehouse caretaker. Thinking nothing of it, Willem accepts, but he soon realizes that these weapons are actually a group of young Leprechauns. Though they bear every resemblance to humans, they have no regard for their own lives, identifying themselves as mere weapons of war. Among them is Chtholly Nota Seniorious, who is more than willing to sacrifice herself if it means defeating the Beasts and ensuring peace. Willem becomes something of a father figure for the young Leprechauns, watching over them fondly and supporting them in any way he can. He, who once fought so bravely on the frontlines, can now only hope that the ones being sent to battle return safely from the monsters that destroyed his kind. [Written by MAL Rewrite]

They say that the more things change, the more they stay the same, and those words could not be more true for the student council of Ousai Private Academy. Though an entire year has passed—bringing the senior members to their final year of high school—not much has changed. President Shino Amakusa is just as perverted as ever, Secretary Aria Shichijou still refuses to put on a pair of panties, Treasurer Suzu Hagimura has yet to grow an inch, and Vice President Takatoshi Tsuda is still stuck as the straight man to their crazy antics. Of course, limiting the fun to a four-way might get a little stale; although the group still messes around with the Judo Club and the Newspaper Club, more girls have come to get in on the excitement. Takatoshi's sister Kotomi, a new student at Ousai, is as perverse as the president, while Uomi, the aloof student council president of the nearby Eiryou High School, fits right in with the insanity at Ousai. With loads of absurdity and sexual humor that keeps on coming, Takatoshi needs to harden up if he is going to keep up with all the madness around him. [Written by MAL Rewrite]

Before Saitama became the man he is today, he trained and fought endlessly to become a hero. While every scuffle leaves his tracksuit uniform in tatters, he always has it mended for free thanks to his local tailor. One day, however, the tailor informs him that he must close up shop due to pressure from a local gang. Saitama decides to help him out—and gains something irreplaceable in the process. [Written by MAL Rewrite]

Specials included in the Blu-ray and DVD releases of One Punch Man.