The anime's opening provides a good example during the sequence where Tomoko is posing like a prison inmate. After a couple frames, Tomoko flashes a Slasher Smile. A half-second later, she lunges forwards and claws the camera with a crazed expression on her face. The semi-stop motion way the sequence is animated, plus Tomoko's stringy black hair, bring The Ring to mind. Tomoko's actual character is hardly intimidating, but still...
Some of Tomoko's expressions are unsettling, to say the least. For example, in the first episode, where she threatens Tomoki that she would kill herself if he didn't talk to her. With the aforementioned expressions and dark atmosphere, it makes it seem like she would seriously kill herself.
There's also Kii's unsettling Death Glare in Episode 8, which even scares Tomoko.
The scene where Tomoko applies for a job in a cake factory, which turns out to be nothing like she imagined it. She's put on a darkened assembly line with masked workers all around her, surrounded by roaring machinery, and can hardly function due to stress.
The way KabukichÅ, the Red Light District Tomoko goes to, is depicted is very unsettling. The whole place is riddled with shady-looking people, including one man who keeps approaching women with an obvious Model Scam in mind, illegal items are being openly sold on the streets, and there are bright neon lights everywhere that make everything disorienting. While nothing happens to Tomoko and she quickly leaves after realizing how in over her head she's getting, there's still a feeling that she's somewhere she really shouldn't be in and she's in very real danger.
Sachi Mima's initial appearance. Not just as a faceless background character, but as a more fleshed-out person. Seeing Koharu hanging out with Shiki Futaki and her club gave her all she needed to single-handedly cut ties with her friend group of her, Koharu, Nori, and Maki, all because she didn't like the latter two. She gives a happy sneer to Koharu, instigates some nasty insults towards Fuuka for supposedly being loose, and then takes advantage of a faux pas Koharu lets slip, to let their friend group dissolve in an instant. And she let the group end on a whim.
While she has been slightly neutered in later chapters due to re-establishing a curious rapport with Koharu, as well as finding herself attracted to Tomoki, any time her featureless face reveals her dark, empty eyes, typically paired with her nasty attitude towards other girls.
