ok, this manga just got wayyyy more interesting.
My theory: Whatever Rinko does will affect the future, although when something does change it's when she skips back and forth from past and future. I think she has to keep on redoing the past to finally get the future she'd always wanted, which was with A-chan although in this chapter I'm not sure if this is the right one since she's been there for a week and A-chan seems happy with her actual nice husband. So, the futures so far: Rin-chan not confessing to A-chan = slut A-chan, Rin-chan confessing to A-chan = sadness, but a seemingly happy ending for her and A-chan. Although this chapter can't be the one ending since I'm not expecting this manga to end in just a few chapters