I would have been totally fine with the first volume being a one-shot. Honestly, opening up the series tab to see this had four more volumes knocked an entire star off. 

I found Mio to be just a little bit annoying— I felt for him, but he didn’t seem to actually grow that much when he went away with how he was behaving when he returned, and maybe it’s the asexual in me but his obsession with being a good sex partner when Shun never gave any indication that he needed or wanted that from him was a very confusing storyline. The premature ejaculation scene was funny as hell though.