I agree with user who thinks this is actually sailing, but with Koyuki's personality I cant actually imagine how the author is gonna land the yuri.
About the subtext discussion, I mean, I see what the point of the tag is, but as a person who has been in love and who has gone through pretty much same things as Koyuki, it is kind of annoying that they are saying one's feelings are "subtext" still, this is manga, and what is obvious for the reader may not be so for the characters and at the end of the day there are mangakas who force the characters do their binding, instead of letting the character decide where the story is going ...and I guess this is just me rambling xD