>>2472421they didn't had sex or kissed, yet they were definitely a couple, i think that Misaki wanted to truly feel loved because she never believed in love that is showed on the panel where she is sitting with their parents and none of them give a shit about each other. she wants a meaning to keep living and she thought many times that through love she could have some meaning in life. it's a really complicated relationship to analyse since they are both very complex characters.
in my opinion they had strong feelings towards each other and had an unbreakable bond. they repeated many times to each other, they need each other to keep living because no one will truly understand their despair and unhappiness towards life in general and their hardships to fit in.