WARNING: The following contains spoilers for My Hero Academia Season 5, Episode 17, "The Hellish Todoroki Family," now streaming on Funimation, Hulu, and Crunchyroll.
As the Todoroki family drama continues to take center stage in My Hero Academia, the series appears poised to address an enduring family mystery. While Endeavor's past abuse of his son, Shoto, and his wife, Rei, is well known, Season 5 has explored the lives of his other children, Fuyumi and Natsuo.
However, previous flashbacks have revealed there is a fourth Todoroki child who has never appeared in the present and is seldom mentioned. The final scene of Season 5, Episode 17 provides a glimpse of the missing Todoroki sibling and hints at what may have happened to him.
When Endeavor receives a message from his daughter requesting a family dinner with Shoto's friends, he is hesitant to accept and recalls what happened at the previous Todoroki family meal. Even though Fuyumi and Shoto appear to be open to the idea of forgiving their father, Natsuo can't let go of his hatred. In a long-winded rant, he cruelly reminds Endeavor of his abuse of Shoto and Rei. He also brings up the missing Todoroki child, confirming this sibling is the oldest one of all and that Natsuo blames Endeavor for what happened to him.
Although this revelation isn't news in My Hero Academia, Season 5 Episode 17's final scene does provide additional context to Natsuo's previous rant. After the drama has died down, Endeavor is seen sitting in front of a shrine, talking about his dream to see his family together at the table again, and happy. A portrait of a boy is shown, whom Endeavor wishes could be there in his dream, identifying him as Toya, the missing Todoroki child.
Endeavor having a shrine to his eldest son with a portrait of Toya as a child strongly implies that the missing boy has passed away. If Natsuo's words are to be taken at face value, then Endeavor's sins are worse than imagined if he is indeed responsible for the death of one of his children. However, the harsh accusation does not draw a reaction from Fuyumi or Shoto, so it's possible they don't agree that Endeavor is to blame for their brother's death.
Very little is known about Toya Todoroki in the My Hero Academia anime, and the circumstances of his apparent death appear to be highly complicated. Considering only Natsuo appears to blame Endeavor for whatever happened to Toya, his accusation might be slightly biased, if not entirely false. In his private moment with Toya's portrait, Endeavor mourns but shows no indication of guilt or regret, leaving the circumstances of the incident still unclear.
In Season 5, Episode 17's post-credits scene, a villain is seen being released from prison and appears to have a personal vendetta against Endeavor. It's unclear if this inevitable conflict from the past will have anything to do with what happened to Toya Todoroki, but Endeavor will be facing his past one way or the other in Episode 18. And for anyone too impatient to wait for the anime to resolve the Toya Todoroki mystery, the My Hero Academia manga has already revealed the answer.