Is she striking to stones together?

macrawr said:

Is she striking to stones together?

Seems like the kanji 切り火/Kiribi is an indication.
I tried looking around and from a website that sells lighters with the same name, they have an origin story which is interesting to know:

From Kiribi Lighters:

The origins of Kiribi lay in the traditional Japanese practice of casting sparks upon a beloved traveler’s back, in order to impart fortune and ward off evil, blessing them on their journey. The practice hearkens back to the famous 8th century legend of Prince Yamatotakeru, and the aunt who gifted him the firestone and striker which saved his life along perilous travels. [...]

I get that this is a momentous occasion in Mahiro's rehabilitation, but isn't that a bit much?

AutumnZephyr said:

I get that this is a momentous occasion in Mahiro's rehabilitation, but isn't that a bit much?

It is, that's kind of the joke. The writer is overplaying the reaction not only to make it funnier but also to portray how momentous it is as well as how rare an occasion this is. Remember that Mahiro hadn't gone outside in two years at the beginning of the story.