kitsunesuccubus-chan
After childhood friends, Christopher and Kitsune, reunite after years of separation, the former can't help but feel a sense of animosity towards her. She left him alone- forcing him to suffer the many hardships of his life all by himself, with no one to talk to.
As a messed up form of revenge, he starts subtly taking jabs at her for it. But of course, it escalates. It gets worse and worse before finally, he sees her again at the subway station.
And then realizes that her emotional state wasn't at all as stable as he thought it was- as he almost, in a metaphorical sense, pushed her off the tracks.
Something that, if he wasn't careful, she'd do to herself in a literal sense.
(Content warnings include mentions of depression, attempted suicide, and maybe self-harm. Do not read if any of these topics are sensitive to you, and take care.)