It's hilarious how the yin-yang symbol (even recycled with the stuffed cat toys) is being used to convey Shiki's alter, acting as her "partner in crime," and the other half of her dissociative identity disorder (is it made up? It's certainly an exaggerated phenomenon in fiction). The film presents a conflict of halves between what can be characterized as a noble samurai on the light side and a perverse serial killer on the dark side. The detective even states, "some kind of symbol was etched upon the body." Yeah, it's obviously a yin-yang symbol, dipshit. How could you miss that?
The male lead is a dope for not realizing the obviousness of the situation with his yandere sort-of girlfriend, even after his "bunny rabbit" admitted many details implicating her as a potential culprit and stating that he would probably die if he didn't stop sniffing after her tail like a dog in heat. He even stumbles upon Shiki playing with the blood of a corpse, wets his pants in fear, and is like, "Ungh, I can't turn my waifu over to the police. Maybe she'll be my girlfriend eventually! She told me that she wanted to kill me. That's so intimate and means she's totally into me! It's so exciting thinking she might kiss me one second and gut me the next!" probably followed by wetting his pants again, this time in ecstasy. What a fucking degenerate. It doesn't help that Shiki is such an unpleasant personality, making this unacceptable as waifubait, meaning we're just left with schizobait (sigh, just to prevent an akshually, yes, I know the difference between schizophrenia and dissociative identity disorder). The latter half of the film, where the male lead is standing outside in the cold upon the premises of his waifu because she is ignoring him (or maybe he's trying to cockblock her kill streak) reminds me of that John Cucksack romcom garbage Say Anything, when Cucksack stands outside the girl's house and holds up his boombox.
Frankly, serial killers are mostly a sensationalized media construction by the U.S., whether it's some MK Ultra or other spook psyop or just a means to close cold cases. A lot of the body counts have little evidence to tie them to a particular killer, often only having a modus operandi in common, most of which are not especially unique... in fact, the bulk of the alleged body count of any particular serial killer is not even unearthed (very few of them carefully keep all the evidence collected under their house, like John Wayne Gacy), merely attributed to them because they claimed them to up their infamy, and a higher body count, more inventive methods, and an interesting story leads to the serial killer being more popular; it's already common for nutbars to call in and take responsibility when they verifiably had nothing to do with the act! One could even liken serial killers to a pantheon of dark gods, committing outlandish acts to enthrall and grow their followers, which gives them strength and love letters in their shrine (prison). Of course, it's glamorized in such a way that a person who would never have a place in history is immortalized by pointlessly killing a bunch of people by means of a discernible pattern, memeing the behavior into having a tangible existence it would never otherwise enjoy, only to be snuffed out by DNA, CCTV, and voluntarily opting into carrying a spy device everywhere (the smart phone). Man, I'm sick of serial killer plot lines. So trite, just like this film and psychobot anti-waifu.
For the reverse scenario of a female getting wet over a serial killer or murderer in prison, in which we have a cuck male falling for a female serial killer (the guy would definitely qualify to be the president of the Yuka Takaoka fanclub) who could and maybe even would turn his spine into a Christmas ornament, The Garden of Simpers Chapter 2: A Study in Hybristophilia - Part 1 is perhaps the ultimate vicarious experience. What a deranged, embarrassing romance, where the young lovers whisper sweet psychobabble and pseud philosophy 101 into each other's ears.
