I was thinking about this single glove that Sumin gave to Seju and whether she still has it with her and your theory actually makes a lot of sense.
Other, much more simple one can just suggest that the story is called One because Seju, after long years is not just finally on her own, but is also living her life for herself for the first time, without her family and ex-girlfriend as a part of the picture. Although I like the mitten theory more, especially the part about holding hands
I was thinking about that too! I'd really like to see her grow and live for herself now that she's left everything behind, I'm really excited to see how her story goes from here
yeah, I just hope that the next chapter we get will be the beginning of One
Probably more of a theory, but I wonder if "One" is supposed to indicate the single mitten Sumin gave Seju, I was wondering why she only gave her one, before realizing that the title could be connected (like how Seju moves on and how her love turns into left over feelings in the same way she tells Sungji that's what the mitten represented) I wonder if it' supposed to also mean something like, having found someone to hold the other hand without one (because she left a journal with her sticker booth photo with sumin, as well as sumin's last note seeing her off, but we never saw her leaving the mitten)