One fairy tale discussion, with lots of symbolism on the side, coming right up!
Among other things, fairy tales are a way of communication to Komari. She’s writing fairy tales herself, Takuya spent a lot of time reading and writing some for her, and Riki could finally get through to her and cure her from her affliction by ways of a fairy tale (and a hug. That stuff’s magical).
Komari talks a lot about fairy tales during the shooting star viewing. She doesn’t like sad fairy tales. The fact that many fairy tales as we know them today have been rewritten and given a more pleasant ending shows that many people feel the same, she concludes. Even “A Dog of Flanders” supposedly got an adaption with a happy ending. She describes it as “helping” or “saving” the sad story. What Riki did for Komari in the end was the same, only that he didn’t hide the sad parts.
Komari’s broken state can be described as a failed attempt at rewriting her story. But while the sad things could be forgotten, they could never be erased and made her suffer all the more.
I’ll focus on a certain fairy tale that’s particularly significant for Komari: The Little Match Girl.
To put it short, it’s story about a poor girl freezing to the death on the street in the night of New Year’s Eve while seeing a shooting star and a series of pleasant delusions, including the reunion with her dear late grandmother.
(The tale is rather short, so you should give it a quick read. There’s bound to be more connections to be found between the tale and Komari’s route than what I’m adressing here!)
It’s from this fairy tale that Komari has learned the concept of “death”. She started associating shooting stars with it. Thanks to Takuya, she doesn’t hate them, but she never forgot the association. She does associate them with one other thing: wishes.
In the epilogue, Komari presents Riki’s/Takuya’s fairy tale, the last page of which she had drawn herself. The fairy tale where she is the main character. On that page, she disappears. With this, and her commentary that “it’s not only sad,” Komari shows that she… well, what exactly? Do you think it’s a sad bittersweet thing like what @BlackHayate02 suspects?