I didn't quite get the significance of the letter in Shiratori's pocket -- anyone's got an idea?
Also, I wonder what happened to the Sunflower Girl? I don't like that ominous picture of a train the last we hear of her.
So, I have a theory; going back to the previous chapters when Shiratori first starts having flashbacks, it seems like there may have been some sort of romantic element? The crossed-out speech bubbles mention "I can't respond to those feelings," which is... Idk. I'm not even sure who's talking in that scenario.
Now, this is a wild leap but I wonder if Shiratori was actually the one interested in sunflower girl, and she had gotten her hopes up ("oh soon this girl will be going to college w/ me so maybe we could be together")? And the letter in her pocket was like. A confession? I have very little evidence for this being the case other than Shiratori's extreme reaction to the news.
I'm hoping this part of the story gets discussed a bit more!