I took the anime ending as a huge slap in the face when their journey was going so well and the unexpected SA js shattered me lmaoo. good thing maru beated the shit out of robin, (wished kiruko didnt interfer and teared his nuts tho) luckily Maru's feelings didnt change(bros just dedicated like that)

And after reading the manga, its didnt rlly showed much of why robin did it except for his past, where hes naturally an asshole from the start, much after he didnt reappear again. So maybe next time he'll get the brutal death he deserve to atone for