It seemed my reply got eaten. Anyway, I saw the comments and thought I would read from the beginning. This is a story that seems a fluffy romance if you look at it from Hikari's perspective but if you step back there is some troubling shit here. First, Hikari has created a fictional relationship in her mind. No where does Ta-kun show any interest in her romantically. Not only that, if you see her behavior it is really stalkerish. She eavesdrops, spies on him masturbating then looks through his room for the magazines, treats him terribly on many occasions like when he wanted to let her use his umbrella. Her friends even find her detachment from reality cute.
The last chapter has been foreshadowed throughout the story. Also, poor Ta-kun is a stand-up dude. He apologizes for making the kouhai sad, is completely honest with her, and even walks her to the train even after she barged in on his dinner. Meanwhile, they use the trope of barging into the chilldhood friend's bedroom to show how it actually can be really a sign of something more like stalking. Good writing. I hope it gets picked up.