Okay im lost. Three characters : Okuzono, Yamashiro, Utsugi. Who loves who??????

Utsugi loves Okuzono from ten-years ago. Okuzono loves Yamashiro since they both were in high school. Yamashiro loved Okuzono but after his heart attack realized it was time for them both to move on. So, in the end Okuzono falls in love with Utsugi.

Utsugi and Yamashiro, it seems, have no romantic feelings for each other, but they use each other in order to bait Okuzono.

There is a lot of manipulation going on, so it's hard to say. But I think this is how their relationships boil down.