aish from where to start, first off haven't read the manga and after watching this, very intrigued to find out how it differs from the movie and if the ending (if it has ended in "written" form) is much more satisfying then this open ending.
secondly, read comments saying - agreeing with Otomo when he called himself self-centered - and i Don't agree - yeah there a bucket load of messed-up, complicated character's here, but he just another one on a long list. he for sure aint at the top of that list.

this whole drama is about people not being perfect in any way, shape or form... trying to succeed at love and life and basically buggering it all up - to put in mildly. if anything watching this if there is anyone that i rooted for by the end, it's Otomo - yeah he was guarded and stoic, the typical tsundere (without any background info about why he is the way he is - i can't say what is the cause for his turning out the way he did) but he for sure aint heterosexual, he either bisexual, pansexual or a deeply closeted homosexual... cause the way he noticed Imagase in their collage/university days, wasn't platonic in the least - and he was always aware of him..

Imagase "proposal" starts to break down his walls from the first encounter. and i think its more about being with a man then being with Imagase - which of course changes when Imagase keeps at it - or maybe i'm wrong, as no one would go back to the woman they r cheating with, when they know their wife has a detective tailing them - that was kind of an open invite, for the 2nd encounter to happen -
the rest is kind of a emotional roller costar, where Imagase who seems to know what he wants, can't deal with getting his wish - and keeps pushing Otomo away with words and actions... therefore the sad open ending

but this is one hell of an emotional ride where u see Otomo grow, mature into his own. and that in itself made this worthwhile - i enjoyed this even if i would've loved a happy end - but "they" kept it real and i can appreciate the reason, as in life no happy ending guarantied.