I haven't read something as confusing as the first couple of pages in a while. The narration at the start makes it unclear whether the first page is a flashback. "If it is, is the confession between pages 2 and 3? If it isn't, is page 3 an unmarked flashback? Why does Fuu-chan shout she's going to kill Fuu-chan and then herself? What uncle?" And so on. Took me four or five reads to get it straight.
The first page isn't a flashback- Haruka confessed to Fuu-chan, and after a day of Haruka avoiding Fuu-chan, Haruka came over to Fuu-chan's house.
"Uncle" is something people cry out when they want mercy.
It can be hard to tell where the arrows are going, but Haruka, the confessor, is the one who makes the murder/suicide threat.
I'm not sure whether the emotional blackmail was intended, since if a friend confesses their love and gets rejected, it's common for the friendship to never go back to normal(e.g. Sayaka and Touko). As such, while the relationship isn't exactly healthy, at least not at this point, I can sympathize with Haruka feeling on edge about the whole thing, since if she gets rejected, she'll likely lose Fuu-chan's friendship, not just the chance to go out with her.