Kiribi

Kiribi is a traditional Japanese practice of casting sparks upon a traveler's back, imparting good fortune, warding away evil, and blessing them on their journey. The practice hearkens to the famous 8th-century legend of Prince Yamatotakeru, and the aunt who gifted him the firestone and striker that saved his life on perilous travels.

Fire is associated with purity, a belief originating with Zoroastrianism and assimilated into Buddhism.

Terminology
As Japan has little flint, the hiuchi ishi ("firestone") is usually meno (agate) or sekiei (quartz). The steel striker in the set is called hiuchigama in the Kanto region and hiuchigane most other places.