Even so, this incident... You called it something like "Imperishable Night," right...?

That's far from its true nature...

Since the moon is unfulfilled, isn't it the Unfulfillment (obesity) Incident? Yukari uses an unconventional kanji / word for "unfulfillment", which makes it sound exactly like "obesity."

I was planning to extend the night until the incident's resolved, but...

Yep.

And those who made the imperishable night end are...