This was horrible!
Messed up, sure... Horrible? Well... If someone isn't only into it for the "pure" (fetishist's?) yuri, then considering that at least Mio is apparently Bisexual
(though everything points toward that Sakura may also be), it was a possible way for her to get out of that situation. Which would've worked better if there was no real other love interest (of either gender) to keep their bond more romantic. While I thought this through, however, I realized that Mio was actually Cheating
on Masato (the guy) at the end. At that point it started becoming horrible for me too, instead of just ignorable.
Their relationship's problems (miscommunication, lack of confidence, dealing with hetero-normative external and internal expectations), while the realistic kind I don't really like to see in manga in addition to the real world, were interesting, and could have been solved better. I don't like soccer either, though, so I don't mind that I have no reason to read it again because of a better story.