A limiter (リミッター, Rimittā) is a term coined by Dr. Genus for his theory on explaining Saitama's strength, which defies common sense. No matter how much effort is put in, there will eventually be a point where a being stops growing. According to the theory, this growth limitation is placed on every being by God so they do not acquire so much power that they are overwhelmed. However, it is possible for the limiter to be removed somehow and an individual can achieve heights far greater than what should be possible.
Gyoro Gyoro is very aware of the concept from the results of his experiments, although he does not use the term "limiter" as Genus was the one who made it up. he simply calls it the limit of growth (成長の限界, Seichō no genkai).
Removing the Limiter
In rare instances, it is possible for certain individuals to remove their limiters. Genus claims that this requires certain conditions. Becoming a Mysterious Being is not the same as removing one's limiter: It is a mutation triggered by negative emotions, experimentation, or environment and the individual is reborn as a new being with a new limiter. Abnormally powerful humans such as the heroes always had the potential to become extraordinarily strong, and those who modify their bodies must modify again in order to improve beyond their natural limitations; they also have not broken their limiters. Saitama, a man who has supposedly broken his limiter, was an ordinary person with no talents or potential, but through effort alone, he evolved beyond his natural limits and achieved power that Genus is unable to even fathom. However, he became bald on top of feeling alienated with his overwhelming strength.
Gyoro Gyoro's Method
Gyoro Gyoro seeks to create the "strongest monster" by breaking its limiter. He found that simply transforming humans into monsters gave them "no prospect of further growth" afterwards. After many failed experiments, he managed to find a way to seemingly overcome this limit: overload the body and spirit of a human by pushing him or her to the brink of death repeatedly, with the intensity tailored to the individual. Despite how simple it sounds, death can occur at any time in the process, and even if one survives, they might lose their minds, rendering the monster "mediocre." Although Gyoro Gyoro had made several monsters that grew fairly powerful this way, most of them eventually died before reaching Disaster Level Dragon. He does claim to have one success though: Orochi, the Monster King.
He attempted to repeat the process to Garou by sending a bloodthirsty Royal Ripper and Bug God to tail him, knowing that they will fight him to the brink of death. These conditions, alongside the many other near-death battles Garou has fought, allowed him to seemingly break his limiter and become an immensely powerful monster that continuously grows stronger, just like Orochi.
During Garou's battle with Superalloy Darkshine, there is narration stating that "Garou's limiter [...] seems to be breaking!" Garou also mentioned that his body felt light as if his "spirit" was removed from his body. He experienced explosive growth and quickly increased his speed, strength, and other abilities. Even while in the midst of battle, he could even adapt to psychic abilities. When he punched Golden Sperm, the latter remarked that Garou's punch was many levels higher than what humans are normally capable of. In the end, however, Garou began running out of fumes and lost the power he had gained. Whether this means that he had failed to completely remove his limiter, that his limiter was placed back on, or some other reason remains unclear.
- Different phrases have been used to describe removing the limiter: Dr. Genus says Saitama "removed his limiter" (リミッターを外す, Rimittā o hazusu) and "broke his limiter" (リミッターを破壊する, Rimittā o hakaisuru); Gyoro Gyoro says she wants to "break the limits of growth" (成長の限界を破る, Seichō no genkai o yaburu). Since they are all used in the same context (Genus even uses both "remove" and "break" in the same conversation), they are all interchangeable.
- It is possible that the "God" Dr. Genus refers to is the same being that Homeless Emperor calls God.
- In the webcomic, Psykos does not know about the limiter; Orochi does not exist in it either. She also had no direct involvement Garou's limiter, unlike in the manga where that is actually her intention.