Ast and Zen, Inosuke, and Tanjiro found a pretty crystal at a thrift store until Ast and Zen were shunned w/ a bright light and turned into kids

Tanjiro: "oh.my.god."

Inosuke: "..huh—"

Ast looks up at them and holds Zen's haori cause, well theyr kids and they have no memory of Tan and Ino