Soul

Soul is the Quirk used by Rody Soul.

Description
Soul manifests itself as Pino, a small pink bird-like creature, and is always active. Pino is connected to the user's soul and her actions articulate their true thoughts and feelings.

Weaknesses
Due to Soul's nature, Rody is effectively unable to lie, as Pino would reflect his inner feelings, which may be different from the one he is expressing.

Usage
Rody gets embarrassed when sharing his Quirk's function to other people, however, Soul was deemed a great Quirk by Izuku Midoriya.

Despite being unable to lie to other people, Rody can use this to his advantage, most notably when he uses Soul to feint his actions. This is demonstrated during the final fight against Flect Turn, when Rody was seemingly about to betray Izuku, but Pino revealed that his actions were a lie.

Due to also being a living creature, Rody is capable of giving Pino directions to act upon, such as used her as a distraction in his chase against Izuku, and using her to input the deactivation key while he was barely conscious. Pino is also able to act on her own, in accordance to the real feelings of Rody, as was the case when she woke Izuku up when Rody took off with the briefcase, representing his desire to want to be stopped.

Trivia

 * Despite Rody being male, Pino is referred to as a female.
 * Soul is the second known example of a Quirk taking the form of a living being, the first being Dark Shadow.