The concept of quirks and how they function is one of many points of intrigue for My Hero Academia fans. Quirks and the power system that they create are fascinating for many reasons. They mix and develop with every generation, usually passed down from parent to child. As this happens, the powers get stronger and more complex, to the point that there’s an in-universe doomsday theory about it. They work like muscles or organs and, as such, there are issues when one’s body was not made with the quirk in mind.
In terms of quirk genetics, the most interesting cases are ones like Eri’s. Her overpowered quirk is called a mutation because nothing similar to it exists in her family tree. This is not to be confused with the mutation, or heteromorph, quirk type. Where one mutates the body in a supernatural way, like Hawks’ wings or Spinner’s reptilian skin, the other is a mutation of the quirk gene itself. This is exactly what happened with Eri’s power. It was unexpected and, because of this, it shattered her family. The same thing happened when Shigaraki’s quirk manifested, though there are theories that he truly was quirkless and One For All gave it to him. However, it’s possible that another beloved character shares this situation. Because of the nature of her quirk and how it was shunned, Toga’s may likewise be a mutation.
Toga’s quirk is simple to activate and perfect for stealth. After consuming another person’s DNA, she can change her appearance to match theirs and, later on, can even use their quirk. This is just like how One For All needs to be transferred via DNA, but her particular method is what makes it unique: she needs to use her target’s blood. This aspect immediately connects her to her inspiration Stain, as he too had a quirk that required blood to use. However, blood isn’t completely villainous, as Class B’s teacher Vlad King also uses it.
This proves that blood-related quirks aren’t rare. It’s therefore most likely that one of her parents has a related power in their family history. However, her backstory suggests otherwise. In the brief look into Toga’s past from Season 5, it’s clear that Toga’s quirk was despised by her family from the moment it activated. Her parents yelled at her and asked why she couldn’t act like a normal girl. In the real world, this is a perfectly reasonable response to finding one’s child sucking the blood out of an animal. However, My Hero Academia takes place in a world where people can split themselves into pieces or make explosions from their hands. Doing “unnatural” things is natural for the common man, but what these things are can usually be predicted.
Toga’s Parents’ Reaction to Her Quirk Is Unusual
People with fire quirks can expect their kids to set things on fire. Those with heteromorphic quirks can expect their children to look like them, even if their quirk is different. People with blood-related quirks should expect their child to follow suit, but this is not how Toga’s parents act. They’re shocked and disgusted by her, wishing that she would be anything but what’s in front of them. In a way, they’re like Eri’s grandfather, not knowing what to do because her quirk is a complete unknown. Whether completely different powers run in the family or they’re some of the minority who are still quirkless, Toga’s quirk seems to have been a shock to her family.
While very little is known about Toga’s family, what has been provided paints a certain picture. Her family could have easily been one of a wealth of people with vampiric quirks who knew how to handle it manifesting in future generations. Instead, she was called a demon child and commanded to hide her quirk. A possible explanation for this is that Toga’s quirk was a mutation that no one could have seen coming.