Second Self is a research hypothesis: when outward appearance changes, how a person feels, acts, and interacts may change with it.
It pairs with Second Identity. Second Identity is who a person is recognized as by others; Second Self is how one feels and acts after becoming the character. One faces outward, the other inward, and the two are tied together.
Several kinds of change can be observed. The most direct is where a compliment lands: “the character is cute” is experienced as “I’m cute.” The meaning of the same interaction changes too: being called cute or patted on the head makes one shy and want to pull away in everyday appearance, yet becomes something to look forward to in character — a kind of Situational Permission. The change does not depend on anonymity; it holds even when the other person knows who is under the head. The easiest moment to observe is the Mirror Moment.
Second Self is not a second personality. It requires neither a separate self to emerge nor the character identity to stay stable over time. What remains after the head comes off is still an open question; even if nothing does, joy is a value in itself.