昔

Refers to a time in the distant past, often implying a significant gap between then and now. It is used to describe eras, childhood, or historical periods. Unlike "mae" (前), which can refer to a very recent past (e.g., "a few minutes ago"), "mukashi" always suggests a longer duration or a different stage of life.

In storytelling, the phrase "mukashi mukashi" (昔々) is the standard equivalent of "Once upon a time," signaling the start of a folk tale or legend.

When used to describe a person's own past, it often carries a sense of nostalgia or a realization of how much things have changed. For example, referring to one's youth as "mukashi" suggests that the speaker now views that time as a distinct, distant chapter of their life.