These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Nightmare Fuel: The show's entire premise, for some viewers. One could probably describe it as "If Parasyte had been a romantic comedy."
Not to mention Ayase's kidnapping: being slowly dragged away in broad daylight, in a courtyard full of students, not one of whom even call a teacher for help, as the kidnappers discuss what they're going to do to (and with) her. Her falling for Seiji is much more understandable in those circumstances.
Values Dissonance: She's stuck to his hand and she's happy about it? Just try pitching that concept in the West...
This sounds less like a case of Values Dissonance and more like a case of Midori's Stalker with a Crush attitude overriding any problems any normal person would have with being in such a situation.
Indeed, when their roles are briefly reversed in the anime, it's clear that Seiji is far less happy about it than Midori.
Not exactly - while Midori is indeed happy with her role at the beginning of the manga, she slowly come to grasps with the harsh reality of needing to return to her regular self. At various points of the story, its made clear to her that being on Seiji's arm not only burdens him (despite his insistence otherwise) but also causes obstacles to their relationship. The entire series is basically showing how she "cures" herself of being aShrinking Violet and Extreme Doormat whose only goal in life is to be Seiji's Satellite Love Interest.
Woolseyism: Kota spews off an idealistic speech about the beauty of understanding, throwing in a reference to the Earth as a spaceship.
Japanese gang member: Shut him up!
English gang member: That's it: I'm killin' the Trekkie!