>>283113763
Nisio hates victimhood (see also: Ill Boy, Ill Girl), but that's not really the point of that particular scene. It's that Harimaze has it in her head "I'm unique. I'm special. I got eaten by a vampire.", while Suicidemaster's like "oh, you mean like a banana? or an earthworm? I met this girl 600 years ago who asked to be eaten like you, too. Oh, and being a vampire kinda sucks, too." She's just completely deflating Hamizawa's view of the situation.
Hamizawa's "only me" line is setting up a (novel-only) scene later where Kagenui is asking who the perpetrator was and Araragi spells out the central theme of the story. Almost every book in Monster Season follows the formula of forcing Araragi to confront something stupid he did in high school. But ultimately, because he'd already outgrown that stupid thing, he's able to solve the situation. Because Araragi outgrew his self-absorbed "dealing with people lowers my humanity" mindset, he was able to solve Shinobu Mustard. His attempts at being more social allowed him to befriend Meniko, who gave him the answer. Him being more empathic allowed him to better understand Gaen and her shortcomings, which gave him the hint about the telephone thing. Being willing to interact with the high school basketball team gave him the insight into Hamizawa's mindset. And understanding that he wasn't special allowed him to realize Hamizawa was going through the same thing and let him plead a case to spare her.
Really, I have no idea how you're supposed to understand any of that from the anime. Shinobu Mustard was a REALLY shit adaption.