While the creators always imply that a development shown in a My Hero Academia movie is canon, all fans know that the events have no real ramifications in the original manga's storyline. However, there is one scene in the franchise's new movie My Hero Academia: You're Next that fans would have wished was canon, and it isn't Dark Might.
As fans must remember, Enji Todoroki was obsessed with creating a progeny capable of surpassing All Might. This obsession eventually led to his first son Toya's supposed death and transformation into Dabi, a development that broke his family. Hence, Shoto never got to experience a normal, fun day with his family members.
Fortunately, My Hero Academia: You're Next movie gave fans a glimpse at the same. Needless to say, this aspect of the movie should have been made canon.
Disclaimer: This article contains spoilers from the My Hero Academia manga and reflects the author's opinion.
My Hero Academia: You're Next gives fans a glimpse at Shoto's dream

As seen in My Hero Academia: You're Next movie, Shoto and others stumbled upon a town center after the Class 1A heroes were trapped within Dark Might's fortress. They were looking for a way out when they saw Deborah Gollinii and Anna Scervino with a line of civilians under the effect of Deborah's Day Dream Quirk.
Deborah had put them under an illusion while Anna used her quirk to touch each of them, causing them to convulse in pain and fall unconscious, surrounded by rose petals. After the heroes saw this, they charged at Deborah and Anna, hoping to stop them. Unfortunately, Deborah noticed the hero students' presence and used her Day Dream Quirk on them.

The Day Dream Quirk effectively saw the heroes fall into a dream-like coma where they lived out what they desired. While characters like Denki and Mineta desired a harem and Tenya envisioned himself as a hero alongside his brother, Shoto envisioned a happy childhood with his family.
In the dream, Shoto envisioned his older brother Toya inviting him to play football during the summer. Soon after, his older siblings, Fuyumi and Natsuo, also chimed in as they wished to play alongside them. The dream then saw all four Todoroki siblings passing the ball to each other and having fun while their parents, Enji and Rei Todoroki, kept an eye on them from afar.

As evident from this segment, despite everything Shoto was subjected to since childhood, he wanted a happy childhood with his family that was never traumatized.
Considering how every My Hero Academia fan dotes on Shoto due to his past, this is one aspect of the movie that would have been best-made canon somehow. Unfortunately, with Toya having passed away in the manga, this scene can never be recreated in the original storyline.
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