Half-Cold Half-Hot allows Shoto to generate ice from the right side of his body and flames from the left.
Half-Cold Half-Hot stems from the fusion of Shoto's father's Hellflame Quirk and his mother’s unnamed Ice Quirk through a Quirk marriage. As a result, Half-Cold Half-Hot is perfectly divided between the right and left sides of Shoto's body. This gives Shoto two powerful separate methods of combat that he may use regardless of the other to an extent, if he chooses.
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 of his flames. This training also helped him learn to use both sides at the same time.
For the Quirk to function properly, Shoto needs to constantly alternate the use of both his sides, heating himself with his left side after using ice or cooling himself with his right side after using fire. Overusing either side might lead to either frostbites or overheating, with possibly fatal consequences.
Right-side: Using the right side of his body, Shoto can drastically lower temperatures and freeze anything he touches.
Shoto is 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 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.
Left-side: From the left side of his body, Shoto can drastically increase temperatures and release scorching hot flames.
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 Arc and talking with his mother, Rei, 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 an impressive scale, although that's not always a good thing, with Katsuki once noting that Shoto loses some of his precision when attempting to overwhelm his enemy.
- Heaven-Piercing Ice Wall (穿天氷壁 Gaten Hyōheki?): Shoto uses his freezing powers to generate a giant, glacier-like wave of ice. He first used this move on Hanta Sero in the U.A. Sports Festival. It remained unnamed until the Final Exams where Momo Yaoyorozu dubbed it. Shoto used a smaller variation of this move against Katsuki Bakugo, and the largest version was used to attack Mr. Compress.
- Wall of Flames (炎の壁 Honō no Kabe?): Shoto uses his burning powers to generate a burst of flames that covers a large area. He first used this move on Tetsutetsu Tetsutetsu in the third round of the Joint Training Battle.
- Flashfreeze Heatwave (膨冷熱波 Bōrei Neppa?): To use this technique, first Shoto cools the air around him with his ice powers. Then, by switching to his fire, Shoto rapidly heats and expands the air around him. This allows him to release a superheated blast.