Izu in general. His entire life has been Hell ever since his mother was killed in a villain attack and his father is nowhere to be found with Izu being sold to the League of Villains as a toddler. When the League allied with the Shie Hassaikai, it made his life double miserable.
Izu's relationship with both Tomura Shigaraki and Overhaul in this. The two young men are pretty much Izu's primary father figures, yet neither of the two has been nothing but abusive towards the boy. Shigaraki and Overhaul made a pet and lab rat out of Izu for years while not caring about his well-being or feelings on how they treated him while cruelly telling him how he was lucky enough to be taken in by the two of them as others would have let a Quirkless child die on the street without a second thought.
All Might's and Sir Nighteye's relationship here is just as heartbreaking as it is heartwarming. While this version of them both had managed to repair their friendship, it can still pull your heartstrings as the canon version of them never had the chance to reconcile their relationship until it was too late with Sir Nighteye dying on his deathbed.
Quirkless children in the foster care system, just in general. They often face discrimination and abuse from their foster parents and getting bullied by the other children just because of the fact they don't have any superpowers like the rest of society.
Izu's nickname here. For most of his captivity, his actual name was changed into something short by the villains who saw and treated him as nothing more than a pet and lab rat with a name that sounded like owners calling their pet.
In A Smile Is Worth Million Words
In Chapter 1, Mirio finding little Izu in a dark room. It's clear that the little boy is afraid upon meeting Mirio for the first time. Izu is described as very skinny and extremely malnourished with his arms and legs wrapped in bandages, not to mention that he's handcuffed to his bed. When Mirio tries not to scare Izu, the poor little guy violently flinches when Mirio tries to get closer to him.
