Telepathy

Melzargard! Return to the ship! The intruder takes priority. Telepathy (テレパシー, Terepashī) is the ability to know what is in someone else's mind, or to communicate with them, without using words or any other kind of physical signal.

Overview
The user is able to read thoughts and speak with others mentally. This ability is primarily used by Espers.

Telepathy is first used in the series when Slugerous attempts to communicate with Kamakyuri which allowed him to learn the latter was killed by Saitama without having to be present.

During Melzargard's battle against the other S-Class heroes, Geryuganshoop is shown using telepathy to mentally communicate with him, telling him to return to the Giant Spaceship.

After Garou awakens from his unconscious state after his battle with the heroes, Gyoro Gyoro uses telepathy to communicate with the Hero Hunter, telling him to stay hidden while he deals with the other members of the Monster Association.

During his battle against Child Emperor, Phoenix Man demonstrated himself to have minor telepathic capabilities, allowing him to mentally communicate with the hero. More remarkably, Phoenix Man is even able to connect his and Child Emperor's spirits within a spiritual space, a place separate from the real world where he and the child hero can talk in peace, even though their physical body isn't there.

While being restrained by Tatsumaki's unrivaled psychic powers, Psykos attempts to communicate with Overgrown Rover using telepathy, asking for the executive's assistance.

18 years ago, after saving Tatsumaki from a hybrid monster, when Blast placed his hand on her head, he saw a vision of Fubuki and could tell that she's her sister. Due to this, it is implied that he may have some sort of psychic or mind-reading ability.

Later, when Tatsumaki falls unconscious due to exhaustion from the battle against Psykos and Orochi, Fubuki uses telepathy to psychically contact her.