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Jigu confesses, and it's very dramatic and emotional, but rather than actually get together right away, they move into a talking phase for awhile. At least that's what Yeowoon calls it, but they have weekly(?) movie dates during this time, and there's some fooling around so ╮( ̄▽ ̄)╭
They don't firmly start dating until the events of the first chapter in Summer, though.
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Uhhhhh it depends. Probably not too long. This chapter (74) coincides with chapter 100 of the novel, and in the novel, Jigu confesses in chapter 105, yeowoon finds out jigu is earthstar in chapter 112 (which is when they officially start dating), they fool around in chapter 113 at which point the bdsm misunderstanding is finally cleared, and then stuff happens and the official story ends at chapter 123, with side stories after that.
Alright someone spill it, who confesses first and how close are we to finally getting them together! (⌒▽⌒)