Shoto was about 5 years old when he was burned. His mother, Rei Todoroki, pleaded with Endeavor to stop their son’s harsh training. “Please stop,” Rei said. “He’s only five.” Considering Shoto appears to be the same age in flashback panels of being burned, he was 5 years old.
In chapter 39, Shoto and Deku face off during the Sports Festival Arc. Deku becomes frustrated that Shoto is holding back and not using the full extent of his abilities, urging him to take control and use his left side. This triggers a flashback to Rei protecting Shoto from Endeavor, his mother saying “He’s only 5.”
Panels that show Shoto being burned seem to be the same age as this flashback, so it’s safe to assume he was still 5 years old when his mother burned him.
How did Shoto Todoroki get burned? His mother, growing increasingly despondent from Endeavor’s abuse of their family, began to see Shoto as an extension of Endeavor. The father put all of his hopes and dreams into Shoto’s success. The Todoroki mother eventually snapped and poured boiling water over Shoto’s face in an act of impulsive frustration.
Shoto Todokoki’s mother was placed into the hospital by Endeavor. More of a long-stay psychiatric type facility, she’s been there for an indefinite period of time. Visitors are allowed, and Shoto has made an effort to rekindle his relationship with his mother despite their incident. He considers his father at fault for pushing her to such a point of desperation.
So that’s it. Shoto was about 5 years old when he was burned. Chapter 39 shows his mother referring to him as 5 years old during the same time period that he received his injury.
Other Thoughts
Shoto was also about 5 years old when his brother, Touya, died. Manga panels show Shoto pining to spend time with his older brother as he played outside with the other siblings, but Shoto kept being dragged back into training by Endeavor.
Shoto’s burn is not a frost burn. The burn came from boiling hot water that was poured on his head.
Todoroki is not blind in his left eye, despite that side of his face receiving burn damage. It is never mentioned in neither the manga or anime that Todoroki is blind due to this injury.
