As with any series that depicts the end of the world as we know it due to Zombie Apocalypse, I Am a Hero is a fertile breeding ground for both Nightmare Fuel and content that's upsetting in an entirely different way.
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- Tetsuko's death is absolutely brutal. She leaves a note telling Hideo not to look at her face if she doesn't have time to put on makeup before dying, and as a ZQN, breaks her teeth on the door to avoid infecting him. Made worse by the fact that Hideo's attempt at Staking the Loved One almost definitely failed, because just cutting off the head won't kill a zombie.
- In earlier chapters, Hideo sees a zombified child on the outskirts of Tokyo eating the flesh of an adult woman while calling out for their mother. A combination of this and Nightmare Fuel, but with a stronger inclination toward being depressing because of the obvious (and uncomfortable) implications.
- The death of the Aokigahara zombie. He still remembers his family and just wants to see a photograph of them before he decapitates himself... Only to get zombified before he gets to do the deed. He only managed to fully decapitate himself after Hiromi gives him the photograph that he wanted to see for the last time.
- Oda's death, and the guilt that Hiromi feels as a result of allowing herself to give into her anger and crush her. Oda wants to die, sure, but Hiromi can't easily forgive herself for doing it out of rage.
- In the chapter set in Pisa, a young girl wanders through the ruined city gripping a plush toy and looking desperately for her family. She's taken in by a group of survivors who it turns out actually didn't survive, causing her extreme horror before she is finally rescued from a Fate Worse than Death by an infected person who retains most of his sanity.
- The fading away of Yajima after Hideo is forced to kill Tetsuko. It feels almost like a death, even though he's just a delusion and does come back later.
- The grandson of the boat captain who rescues Hiromi and Hideo from the Hive that tries to chase them down. He wanted to go ashore with his grandfather for a simple scavenging mission and ended up bitten and infected.
- What happens to Hiromi. After joining the Kaiju-sized monster in Tokyo, one of her last actions as a human being is to convince the thing to let Hideo survive, nominally so that he can suffer more, but really because even in her demented state at the time, she doesn't want to see him die.
- The ending. Not only did Hideo fail spectacularly to save Hiromi from the gigantic zombie golem, he essentially lost everyone who befriended him (Hiromi, Oda, etc.) during his journey for survival, and only managed to barely survive the entire ordeal in the end. At the very least, the only consolation comes in the fact that Hideo eventually manages to build his new life (somewhat) in the ruins of Tokyo and how the remnants of Kurusu's group managed to escape to a safe island, rebuilding their lives anew.
