ENDING SPOILERS AHEAD: The ending is not happy ending. Hideo loses his mind and there are a lot of questions left unanswered but I feel like this was a good ending especially for a Manga like 'I am a hero' where there's no real happy points in the story. The bits that give off the happiest vibe are just the bits where they're ignoring everything shitty going on around them. A lot of people are unsatisfied with the ending, they say that Hiromi should have been saved or that Hideo should have simply just killed himself however I say that the ending was probably the best ending for a story like this. Hideo losing his mind and being alone really fills you with despair and I think that that fits really well with this story. A happy ending would have been totally off from the rest of the story and I feel like a lot of people don't realize that. I AM A HERO IS NOT A HAPPY MANGA. IF YOU WANT A HAPPY ENDING GO READ A SLICE OF LIFE.