Ko Yamori is relatively good at studies and amiable with his classmates, but he puts a lot of effort into maintaining this facade. One day after developing insomnia, he decides to sneak out and take night walks alone. Eventually Ko meets a weird girl who diagnoses the cause of his sleeplessness: despite making changes in his life, he is still holding himself back from experiencing true freedom. She says that he won't be able to sleep unless he is satisfied with how he spends his waking hours. The girl, Nazuna Nanakusa, invites him back to her apartment to share her futon as a way of curing his insomnia, which she claims is her hobby. Unaware that he is only feigning unconsciousness, which he has gotten quite good at practice, she leans over him—and bites his neck!
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As far as first episodes of a vampire series go, this covers very standard staples of the genre. Dissatisfied person meets stranger, stranger turns out to be vampire, person discovers their secret, and their relationship starts from there. Nothing even remotely surprising, innovative, or nuanced.
Vampire is charming (in her weird way), potential victim sees something in the vampire that might change their stagnant life, someone declares their intention to love to the other, and of course the victim's blood is super delicious.
But I do recommend watching the first episode anyway, at least.
The atmosphere of this series is completely different. There's a peaceful stillness to all of it, even with the soundtrack imposing itself at times. There's a vibe of timelessness and a slight chill to it all. I think it perfectly captures that extremely late-night calm that you only get where there's really nobody around but you and your companions. The entire city (or park, or field) is yours, and yours alone. That brings in that little euphoria of catching a moment/place that is up for grabs, and you got there first.