Chapter 301 emphasizes the grim reality of marriages to combine quirks, something considered taboo in this hero society.
The Hero Academy is a manga written and illustrated by Horikoshi Kohei. The story follows Midoriya Izuku, a boy born without superpowers in a world where superpowers are commonplace. Despite this, he dreams of becoming a superhero and is aided by the world's greatest hero, who shares his powers with Izuku after realizing his worth and helps him enroll in a high school for aspiring heroes.
Chapter 301 'Igniting the Wrong Spark, Part 1' delves deeper into a theme previously only briefly mentioned in the series. As Endeavour reminisces about his past treatment of his son Toya, now known as Dabi, Rei finally confronts her shattered husband.
Marriages for Quirks are to maintain the family hierarchy system in the Hero Academy manga society. Rei's family is highly reputable, and they decide to accept Endeavour's proposal to ensure the family's reputation. The marriage of their only daughter, Rei, to Endeavour without her full consent demonstrates how the 'weaker' individuals in society are exploited for the benefit of stronger heroes.
Marriages like these, aimed at creating superior individuals, often have unpredictable outcomes. In Toya's case, he inherited his father's abilities but physically resembles his mother. Therefore, Toya's body cannot withstand the heat from his own flames, causing his body to constantly burn.
However, Toya inherited the ability to survive in freezing temperatures. And this proved effective when he had to confront Shoto. Endeavour gave up on turning Toya into a hero. But he believed it to be his destiny. Or rather, Endeavour's own pride bound him.
The mother suffers the most. Rei was treated as a quirk-producing machine until she achieved ideal results. This is perhaps one of the major reasons why quirk marriages are taboo in hero society. Initially, Rei accepted it for her family. With three young children, Natsu, Fuyumi, and Toya, Rei seemed to be the sole parent to them after Endeavour focused on Shoto.
Marriages combining quirks as told in the story are an interesting idea. But looking deeper into the narrative, it's a gamble for all involved parties. Children will always feel like they were born to serve a purpose rather than out of parental love. While it's uncertain whether they produce superior individuals, it's still a concerning issue. If possible, All For One would have exploited this already.