It's not remarked with a translator's note, so I'll put it here. On the last page, Yamada says "sayonara", which can be translated as "goodbye", but can also be taken with deeper meaning. This was mentioned in the Boredom Society's translation:
In Japanese, this farewell is often used similarly to the French "adieu", i.e.: said with finality.
and on reddit in the discussion of how this chapter was adapted into anime:
Actually the anime does use the specific "deeper" goodbye the Manga described, "sayonara" which gives a greater sense of finality. Its just that the anime can't exactly give a translation note aside for small stuff like that.