Heroes are needed in One Punch Man: World! A sinister wave of monster attacks has left Earth’s cities and the Hero Association under duress. However, after three years of special training, Saitama has become so powerful that he can defeat opponents with a single punch. The thing is, Saitama just does the hero thing for fun, but when every enemy goes down in one punch, overwhelming power can be kind of... boring. Now, in front of the laid-back strongest hero, a new enemy appears. Will he be able to show his full power today?