TodoDeku

TodoDeku is the slash ship between Shoto Todoroki and Izuku Midoriya from the My Hero Academia fandom.

Canon
Shoto began an arch-rivalry with Izuku during the U.A. Sports Festival arc, claiming he would beat him using only his side that controls ice. The reason for this was because he did not want to use what he felt was his father's power, and wanted to prove to his father -Endeavor- wrong in that he wouldn't win with only the power received from his mother. Although in a rivalry, Izuku still admired and respected him, admitting that Shoto was far stronger than him.

Their fight in the festival changed Shoto's ways, and opened him up to massive character development. It is revealed that Shoto's past involved abuse and overworking, with even his mother being driven madly to scarring his eye with boiling hot water. After this, his mother was sent to the mental hospital by Endeavor. Todoroki was devastated by this act.

Izuku was the breaking point that helped Shoto embrace himself, not by making him give into his father's will, but by making him realize that the connection between the quirks of a person and their parents are not what matters most, but being able to recognize it as the quirk that they as a person have. Midoriya even being super shy faced Hero Number 2 (father of Shoto) to defend the Todoroki. One of the most iconic lines stem from this scene, "It's your power, isn't it?!" said by Izuku. Izuku helping him during the fight, even knowing that Shoto was only using half his power and would most likely beat him when accepting his fiery side, was a sign that Izuku cared much more about helping Todoroki than winning.

After the fight, the two became closer, creating a strong bond of friendship. Shouto's starts to show less difficulty in approaching people and demonstrating how he feels. Izuku begins to strive even more to improve his individuality as he becomes more confident.

During Todoroki's fight against Bakugou, seeing that Todoroki due to the emotional state could not use his full power, Midoriya shouts in the middle of the audience "Don't lose! Do your best!" Todoroki listens and feels something that activates his firepower, But in the end, Todoroki can not maintain the fire and because of the defeat, Bakugo does not accept the victory.

After the cavalry battle, Shouto told Midoriya everything he thought, both his past and his suspicions, and after all, both accepted their rivalry, with a Bakugou listening between the two.

In the Vs. Hero Killer arc, Izuku was stuck in a bind while attempting to save Tenya Iida from "Hero Killer" Stain. This caused him to secretly send out a signal to his location on his phone, which Shoto-- although hesitantly, questioning whether he would really be in trouble- was the first and only one to comply and come to his area. Todoroki then saves the life of Midoriya who was about to be killed by Stain.

Shoto became angry on behalf of him and his friends Tenya and Izuku for having trouble against the law despite the fact they stopped a serial killer. They both have things in common - such as their admiration for All Might and the desire to become great heroes - accompanied by their differences.

In Season 3, when Midoriya is in the hospital, Todoroki appears alone to visit Midoriya in the hospital. They have a great respect for each other, always using surnames and, in the case of Midoriya, the "Kun".

Manga
Manga scene developed in the dining room. Izuku is saddened by the events that have happened with Eri and the fact that all the pressure from the mission falls on some of his colleagues and himself. He can not talk to his best friends, and says "Heroes can't cry." Todoroki gives him a serious considerate look and says "Even heroes cry sometimes." In an attempt to comfort him, he offers a portion of his noodles.

Moments

 * During the Todoroki VS Sero fight, Midoriya sensed the feelings of Shouto's sadness, feeling a strong sense of wanting to help him and save him from his tragedy and his past.
 * All Might comment on "Izuku preferred the possible defeat of himself than to see [Shoto] suffer".
 * Todoroki's first word for season three was "Midoriya".

Fanon
The initials "Todo" and "Deku" were popularized by western fandom, while in Japan this ship is better known as TodoIzu. This is one of the most known and fan-supported due to the friendly and noble behavior they both forged in the anime/manga. TodoDeku is the most popular ship in Western fandom, and the second most popular in Eastern fandom. It is the most popular ship for Todoroki in both fandoms. Many who support TodoDeku do not like the ship BakuDeku, and typically support KiriBaku along with shipping TodoDeku.

Fandom
FAN FICTION
 * Izuku/Shouto tag on FanFiction.net
 * Izuku/Shouto tag on FanFiction.net

Trivia

 * They are usually paired in official merchandises.
 * The ship has been featured on the Fandometrics most reblogged ship list several times:
 * It was the twentieth most reblogged ship the week ending April 15th 2019.

Reference
TodoDeku