mc was so fragile, in the surface when he was doing his manga well and having a happy life with his wife, he still carried all the guilt and baggage that spoils everything once he throws it up. with him coming from an extremely cynical perspective about society, its hard to blame him losing it after seeing his wife get r*ped by someone seemingly trustworthy and harmless. his friend also with underlying schnaudenfraud that doesnt get resolved or cleared out, man completely lost his hope for humanity.
to top it all off, he found comfort from a suspicious person and gave him drugs, being a person who was an alcoholic along at a fragile state, his mind was ultimately at its weakest and did not understand any consequence of it, he became too desperate and clung to the euphoric feeling of the speed he'd be injecting himself.
this manga is the very definition of a downward spiral in steroids. with a short moment of redemption but would naturally fall back into the place of the downward spiral as mc's roots are bound for failure and ruin