Warning: contains spoilers for My Hero Academia Chapter 351!
The latest fight in My Hero Academia between Dabi and Shoto has been met with enthusiasm by fans, but the science behind the name of Shoto's latest attack makes it even better. The mangaka for the series Kohei Horikoshi has previously used the names of attacks to give them more weight or meaning, like when All Might unleashed his "United States of Smash" attack after previously only using attacks named after single American cities or states. The meaning behind Shoto’s latest attack name is a bit more subtle, however.
Shoto Todoroki is one of the characters in My Hero Academia who has changed the most since his introduction. Born with a Quirk that lets him manipulate ice on one side of his body and fire on the other, Todoroki initially refused to use the fire side of his body in order to spite his father. Deku was able to help him accept his fire as a part of himself, and much of his arc has been trying to reconcile with his other family members, who all were subjected to their father Endeavor’s abuse. His eldest brother Toya became the villain Dabi, who has vowed to destroy his father’s legacy and burn down Hero Society as well.
Over the last couple of chapters of My Hero Academia, Shoto and Dabi have been engaged in a brutal fight. Each has been steadily escalating the power of their attacks, with Dabi recklessly destroying his body with each successive new technique. Shoto himself unleashes a new ultimate attack at the end of chapter 351, which he calls "Flash Fire Fist: Phosphor." The attack appears to be a fiery punch from his ice side, which is appropriate given the attack’s name.
The attack’s name “Phosphor” evokes two different but related scientific terms. A phosphor is a substance that glows via some process that is not ignition. This may not seem to fit an attack that directly seems to be using fire, but since it is coming from Shoto’s ice side instead of his fire side, it seems appropriate. In addition, it could imply that the attack glows brightly, something that isn’t very easy to see with My Hero Academia's black and white art. The other term it brings to mind is phosphorus, an element with an incredibly flammable form called white phosphorus. Given that this attack is coming from the “white” side of Shoto’s body (based on his hair color) and this attack seems incredibly explosive, this term also seems appropriate. In fact, the reference to phosphorus may reveal an even deeper truth about Shoto’s mastery of his powers.
The other most common form of phosphorus is red phosphorus, which is commonly used in flame retardants. Given that the two halves of Shoto’s body are white and red, this seems like a very intentional reference. Since the red and white halves of Shoto’s body perform opposite functions, referencing phosphorus in an attack name while throwing a fiery punch with his icy side may imply that Shoto has mastered his powers to the point of being able to use them both in tandem. As the chapter ends with him using this attack, fans will have to wait to see its actual effect. By referencing scientific terms with this attack against Dabi, My Hero Academia is thus both making the attack more visually impressive and subtly showing Shoto’s growth.
My Hero Academia Chapter 351 is available to read from Viz Media.