Heal allows Chiyo to amplify and quicken her targets' healing process by extending her lips and kissing them.
With Heal, some grave injuries requiring months to heal can be healed completely in a matter of seconds.
The healing process, however, is not without its cost. It requires stamina from the receiver's part in order to work, leaving said receiver very exhausted after the process is completed if an injury is, or injuries are, serious enough. Heal cannot regrow lost body parts.
If the amount of stamina someone has is less than what is needed to heal their injuries, the process could lead to their death. As such, surgeries and conventional healing methods will be required for severely life-threatening injuries before the effects of the Quirk can be applied. In such cases, it is sometimes applied several times over a period of time instead of healing everything in one shot. This also means that if a person suffers serious enough injuries, Heal will be unable to save them from death. Additionally, Heal is unable to completely heal certain injuries if they are too serious: this was first seen when Izuku Midoriya overused his Quirk against Shoto Todoroki, leaving his right hand scarred, and again when he unleashed his "1,000,000% Delaware Detroit Smash", leaving his arm permanently damaged even after Chiyo used her Quirk on him.
Chiyo travels around Japan in order to help as many patients as possible, utilizing her Quirk to speed up their recovery. Because she is a capable surgeon of her own, Chiyo can treat most injuries by herself.
Chiyo's abilities make her vital for U.A. High School's operation, otherwise the institution would have a difficult time justifying their dangerous exams and events. Chiyo has control over the school's infirmary and other related branches, where she performs her healing procedures on students and teachers.
Chiyo has a complicated doctor-patient relationship with Izuku Midoriya due to the repeated self-harm the latter experiences thanks to his power (the nature of which Chiyo is aware). While Chiyo has no problem treating Izuku for damages unrelated to his Quirk, she absolutely refuses to heal Izuku's self-applied injuries, as a way to discourage him from using One For All recklessly.
- Heal was described as "Super Healing Factor", "Healing", and dubbed by the anime as "Recovery" but its name was revealed in the second databook.
- The Quirk works similarly to Tsunade's mitonic regeneration from Naruto, only it's applied to others and not just the user. Since it speeds up recovery, it also means cell division is also sped up, decreasing the lifespan of the one being healed.
- My Hero Academia: Ultra Analysis: The Official Character Guide.
- My Hero Academia Manga and Anime: Chapter 4 (p. 9) and Episode 4.
- My Hero Academia Manga and Anime: Chapter 11 (p. 9, 14) and Episode 8.
- My Hero Academia Manga: Chapter 231.
- My Hero Academia Manga and Anime: Chapter 40 (p. 14-16) and Episode 24.
- My Hero Academia Manga and Anime: Chapter 45 (p. 4) and Episode 26.
- My Hero Academia Manga: Chapter 161 (p. 7-8).
- My Hero Academia Manga: Chapter 4.
- My Hero Academia Manga: Chapter 21.
- My Hero Academia Anime: Episode 4.