Seeking to have a child capable of surpassing All Might, Enji Todoroki agreed to a Quirk marriage with Rei Himura. When he was 22 years old, his first child, Touya Todoroki, was born prematurely. Although he did not inherit the Quirks from his parents, Touya was born with a fire Quirk more powerful than Enji's own Hellflame, so when the time came, his father would train him. Later that year, his sister Fuyumi Todoroki was born.
From presumably quite a young age, Touya was constantly trained by his father and the young boy was actually quite eager to learn all his father's moves so that he could one day become a great hero. Although none of his children bore the ideal Quirk he was hoping for, Enji was satisfied with Touya and saw him capable of surpassing All Might with his powerful Fire Quirk alone, so he placed his ambitions on his shoulders.
The situation changed drastically as Touya's red hair began to turn white and his body suffered burns every time he used his Quirk. Enji and Rei went to see a Quirk doctor to find out what was wrong with him. The doctor explained that while Touya has inherited a powerful fire based Quirk from his father, he also inherited his mother’s resistance to freezing cold, rather than his fathers resistance to scorching heat, meaning that he would burn himself whenever he used his flames. Because of this, Touya was limited in how far he could safely push himself with his Quirk.
Enji deemed him a failure and suddenly stopped training him. Touya, despite the dangerous flaw in his Quirk, still longed to be a Pro Hero when he grew up. He began to beg his father to continue training him, but Enji refused, saying that it was for the sake of his well being, but Touya wasn't pleased. Later, he talked with his sister Fuyumi and told her that he can tolerate the pain and burns, but little Fuyumi told Touya that she was also worried about him getting hurt. Her words offended Touya, who yelled that she didn't understand him because she was a girl and walked off, saying that his father was the one who lit the fire under him to surpass All Might.
Touya began training on his own, despite his father and sister trying to convince him to stop. Enji lamented that his son also inherited his stubbornness and decided to have more children until conceiving a suitable successor to his ambitions. Rei said that his idea was too cruel, especially considering Touya had finally realized what he wants to achieve through their children, but Enji considered that this plan would finally make Touya give up on his obsession.
The years passed, and Enji and Rei had more children. This would ultimately lead to Natsuo's conception, which made Touya start falling into despair while Endeavor's desire to surpass All Might continued to grow. Eventually, Shouto Todoroki was born, having inherited a perfect combination of both their parents' Quirks. Enji had finally conceived the much desired heir he was seeking, but Touya despaired even more, as Shouto's birth implied that his entire purpose and his father's awareness and attention had just been taken from him. However, Touya was still determined to fulfill his father's dream and refused to abandon it. He continued training on his own, eventually he started going to Sekoto Peak where his father used to train.
Enji told Touya to stop training in secret because he was covered in burns and told him to look beyond the world of being a hero and do things like play with his siblings or make friends at school, saying he can understand that and one day it will all be a distant memory. Touya, however, with tears flowing from his eyes, told his father that everyone at school wants to be heroes themselves, and he couldn't understand what it is like to give up because he has him as a father. Enji lit the fire in him to surpass All Might and it was not going out, just as he calls him by his hero name rather than "father".
Their argument drew Rei and the rest of the children to where they are. Broken down, Touya told his father to look at him, as he violently lashed out with his flames activated at his mother carrying an infant Shouto, attempting to harm his youngest sibling. He was stopped before he could hurt anyone, but after Touya's outburst, Enji decided to ban the other siblings from interacting with Shouto so he can focus on training, and entrusted Rei to look after Touya. When Rei said that all Touya wants is for his father to acknowledge him, Enji replied that all he can show anyone is the world of heroes, to which Rei scathingly replied that he is just running away from his problems.
During the following years, Touya developed what appeared to be an excellent relationship with his siblings, they were always together and they always played together. This is especially true regarding his brother, Natsuo. However, they were raised separately from Shouto. Likewise, his father's traumatic abuse and then abandonment had a strong emotional and mental impact on Touya, and many times he used to go to his brother Natsuo, with tears in his eyes, questioning why he even existed.
Five years had passed since the incident, and Enji decided to train Shouto, preventing him from playing with his older siblings despite Shouto's begging. A thirteen year old Touya witnessed them, and glared at the two of them hatefully. Later that night, he confided in Natsuo his inner doubts, acknowledging it was his fault for attacking Shouto, who did nothing wrong, but rants about his feelings towards their father and how he considers the rest of his children as "failed creations", wondering whether the only thing heroes did was make children and discard them when they didn't need them. Natsuo, however, just wanted to sleep, and suggested Touya talk to Fuyumi once in a while, Touya was hurt by the implication that Natsuo was brushing him off as well, explaining he was the only one who Touya could talk to.
One day, when he was preparing to go to train at Sekoto Peak, Rei tried to dissuade him and make him consider whether or not he really wanted to be a hero, assuring him that there are more options than the hero world. Touya was infuriated by his mother's words, yelling at her and asking if she has been reading any self-help books lately. His statements left Rei surprised as he continued his rant, saying that he already knows she only married Enji because her family was poor and that was the only reason he was born, putting responsibility for his problems on her shoulders as well.
Touya continued to train at Sekoto Peak, and during the winter season, around the time he had a growth spurt, his Quirk developed, and his flames' color changed from red to blue. Touya discovered that his flames are linked to his emotional state and would get stronger if he was riled up. He started crying saying he doesn't know why he does when he gets worked up. Shortly afterwards, excited to show his father how he had developed, Touya asked him to come to Sekoto Peak the next time he had a day off. Enji, however, lifted up his shirt and saw his burn scars, angry that Touya had been training again, but his son was adamant that he was destined for greatness and determined to make his father proud of him. Frustrated, Enji ignored his eldest son's pleas and took his anger out on Rei for not stopping Touya.
Sometime later, Touya waited at Sekoto Peak for his father to meet him, but Endeavor never showed up, much to Touya's disappointment and anguish. The emotional turmoil he felt caused him to lose control of his flames, resulting in a massive wildfire. Touya tried to save himself, but he didn’t know how to quell his flames, as his father only ever taught him how to increase the heat. He was scorched with flames exceeding 2,000 degrees Celsius: his body was believed to have been incinerated, and the only thing that was found was a part of his jawbone.
His "death" affected his family, especially his mother Rei, whose mental state had already been harshly affected by her husband's past abuses, and his brother Natsuo, who still considers his father responsible for Touya's demise. Touya's family installed a Butsudan Buddhist altar in his former room after his passing and still send their prayers to him. Even Enji is seen praying at it, saying that he regrets the loss of his eldest son.
However, Touya did not die but was left with severe burns and grew up without his family knowing the truth. The traumatizing abuse Touya experienced throughout his childhood drove him to become a villain, renaming himself Dabi and dyeing his hair black to hide his true identity. As the years passed by, Dabi secretly observed his father's actions from afar. Accepting his newfound life as a villain, Dabi slowly plotted a plan to ruin Enji's life by destroying his hero career.
