Half-Cold Half-Hot allows the user to generate ice, frost, and cold from the right side of their body and fire, flames, and heat from the left. However, the user is unable to manipulate either element that comes from an external source; they can only create them from their body.
Half-Cold Half-Hot's power is perfectly divided between the right and left sides of the user's body. This gives the user two powerful, separate methods of combat that they may use regardless of the other.
As part of his training, Shoto submerged himself in a barrel of water and alternated between his ice and fire abilities to regulate the temperature of the water. His body becomes accustomed to the cold, and he learns to control the power output of his flames. This training also helped him learn to use both sides at the same time, which Shoto acknowledged he initially could not do so reliably due to having used and became better accustomed to his right side's ice abilities than his left side's fire abilities.
Shoto's later development of Half-Cold Half-Hot has allowed him to generate either element on either or both sides of his body, as well as combining the two into a “Cold Fire“ that simultaneously burns and freezes opponents. This development has effectively turned his one Quirk into two, as well as giving protection from even the most intense of flames.
The user needs to constantly alternate the use of both elements, heating themselves with the left side after creating a great volume of ice or cooling with the right side after generating strong flames. Overuse of either side without the other to regulate their body temperature could lead to either frostbite or overheating affecting their whole body, with possibly fatal consequences.
When Shoto uses Phosphor, this weakness is eliminated for the duration of the technique, as he circulates both heat and cold simultaneously through his body.
Right-Side: Using the right side of his body, Shoto can generate ice to drastically lower temperatures and freeze anything he touches as well as creating solid structures for offense or defense.
Shoto's able to swiftly freeze entire buildings, as well as create large waves of ice instantaneously. Despite its incredible raw power, Shoto possesses great control and direction over his right side. He can restrict the ice to avoid fatally freezing someone, or use precision attacks to freeze only certain portions of a target's body. If fighting alongside others, he is capable of covering enemy territory with ice while simultaneously preventing it from getting in his allies' way.
Shoto is capable of molding the ice and frost into certain shapes to support himself, such as protective barriers, stairs to elevate himself or a moving wave of ice for him to surf through. Shoto has many mobility options too, like stacking ice shards behind his back to propel himself forward or freezing the ground to skate on it.
Prolonged usage of his right side will lower his body temperature to dangerous levels. When this occurs, Shoto's body gets covered in frost and his ice attacks lose their effectiveness. His maximum output brings him to his temperature limit almost immediately.
As Shoto is far more used to his right side than his left, he instinctively begins attacks with the former. This can be disadvantageous against an opponent that possesses a Quirk that is able to counter it.
Similar to his father's ability to raise his heat to its maximum level, Shoto decided to follow this lead and lower his ice temperature to its coldest level. This was first demonstrated when Shoto froze Chimera by drastically dropping the temperature of his ice, and while it was successful in freezing him, Shoto's body could not handle overexerting himself, resulting in frostbites spreading all over his body and knocking him unconscious.
Left-Side: From the left side of his body, Shoto can generate fire to drastically increase temperatures and burn anything he touches.
When Shoto ignites his flames, the resulting blaze covers his arm and the left side of his head. He is able to shoot out consuming streams of fire or protective short waves of it. After upgrading his costume to help him control his temperatures, the flames only ignite on Shoto's hand, displaying more command over his left side.
Due to Shoto's animosity towards his father, Enji Todoroki, he held off on using his left side offensively for most of his life, activating it only for thawing victims of his freezing attacks. After battling Izuku Midoriya during the U.A. Sports Festival and talking with his mother, Rei Todoroki, Shoto finally began to accept and embrace his left side, becoming able to produce large-scale fire attacks like walls of flames. However, despite Enji teaching Shoto from a young age that the flames his son can produce are unrivaled, Shoto still prefers to use his ice more. As a result, his manipulation of flames is still rather poor in comparison to the finesse of his right side. His lack of control made adjusting to the high temperatures of his flames difficult for him as well.
During the Joint Training Arc, when confronted with Tetsutetsu Tetsutetsu, who could resist extreme temperatures and was unaffected by freezing attacks, Shoto found himself having to go past his limit and unleash the full might of his left side. Shoto's strongest flames are hot enough that they threatened to melt Tetsutetsu's Steel body, while nearly setting all of Ground Gamma ablaze. It's possible that Shoto can increase his fire's temperature even higher, but Juzo Honenuki prevented him from attempting so. According to All Might, Shoto's flames at full power are as strong as Endeavor's own flames.
Overusing his fire can cause his body to overheat and induces dizziness that can render him unconscious if not kept in check; a weakness he shares with his father. Endeavor even stated that even though Shoto's flames have the potential to surpass his own, Shoto using his flames at full power is still dangerous, especially if he can’t control them.
Fortunately, Shoto is capable of using his other side to counteract the dangerous effects of whichever one he happens to be overexerting. Activating both sides simultaneously is possible as well, but lack of practice has made this awkward for him as it dulls his movements.
By chilling the air using his ice and then heating it in an instant through his fire, Shoto can release a huge super-heated blast of flame that devastates anything on its path. Overall, Shoto's strongest attacks tend to be of a very impressive scale, although that's not always a good thing, with Katsuki Bakugo once noting that Shoto loses some of his precision when attempting to overwhelm his enemy.
By the end of the war and after training with the Pussycats, Shoto has managed to gain an almost equal mastery of his left side to his right side, bridging the gap of inexperience with his left side due to his animosity towards his father.
- Half-Cold Half-Hot stems from the fusion of the Hellflame Quirk of Shoto's father and an unnamed ice Quirk from his mother through a Quirk marriage.