Insomnia is a serious problem which affects a serious number of people. They go to lie down but can't fall asleep, so they just stare at the ceiling, or they wake up in the middle of the night but can't go back to sleep, so they just stare at the ceiling. Adachi has the worst kind of insomnia. Not only is he unable to sleep at all, he turns into a horrifying monster.
Being a monster in At Night, I Become a Monster does come with its bundle of perks, such as being able to steal into the school at night to steal his forgotten textbooks. However, he isn't the only one creeping into the school at dead o' clock. His classmate Satsuki Yano comes in for what she calls “midnight break,” when the graveyard shift guards allegedly let you do whatever you want, even waltz in as the Pus of Man.
The plot of At Night, I Become a Beelzebub is like railroad tracks: two rails running parallel, with wooden planks connecting the two. Chapters alternate between the nights, when Adachi chills with Yano, and the days, when he ignores her and turns a blind eye to the constant bullying she endures and, worse yet, justifies it. With that summary, it's not hard to see that the title is so rich in irony you could sell it to a mill and retire to the Bahamasv
The contrast of the school between day and night is like...well, it's like day and night, but what's interesting is how Yano herself separates the two, like they're incompatible planes of existence, refusing to carry out any discussion regarding the daytime and holding no grudge against Adachi for his actions—or lack thereof—when he comes to visit during the night.
Yano is a socially inept girl. She has trouble reading the atmosphere of a room, often acts like she's in her own little world, and speaks with frequent pauses. What rubs the lot of her classmates is how she's always got this smug grin on her face, like she's silently laughing at anyone who believes she's beneath them. Her peculiarities lead her classmates to bullying her, and her ostracization is so harsh that anyone showing the slightest hint of sympathy, kindness, or basic acknowledgment of her existence is themselves ostracized.
Despite the hardships she weathers during the day, the night is when she can unwind and destress, and once Adachi shows up, she has another person she can talk to about the things she likes, such as books and music, even if that person is a bystander to her torment. However, her forgiveness of Adachi could be because of her perceptiveness.
The first time Yano meets Adachi in his monster form, she can tell almost right away it's him. He doesn't utter a word and doesn't do more than rummage through his locker, yet she can tell that the eight-eyed, six-legged, four-tailed monster invading her school is her classmate. Yano's got an acute pair of eyeballs in her sockets, and more than once she sees right through Adachi's oozy form to peer straight into his heart, such as when she points out how he's in love with a classmate (though since he doesn't confirm nor deny this, it's up in the air whether she's correct or just spouting what she wishes were true). Her entire class likely believes she's the most dimwitted of the roster, but the truth might be that she's actually the smartest one there, despite her uncoordinated behavior or penchant for changing the conversation at the drop of a hat. I mentioned how she can't read the atmosphere of a room, but I was just quoting Adachi. It's only allegedly that she can't read the atmosphere, because on two separate occasions she turns it to flow how she pleases.
Yano's most defining moment would be near the end of the novel, when we learn one fact about her smug face which recontextualizes her entire character. I won't spoil what, of course, but it's another tick on the list of items that makes you wanna wrap her up in a hug, pat her on the head, and sing to her that every little thing's gonna be all right.
Yano takes the trophies for Most Intriguing Character and Most Sympathetic Character, but there's a pair of runner-ups for the former category. Most of the side characters in At Night, I Become a Wendigo can be described with an adjective and the appropriate gender, such as “nice girl” or “mean boy,” but the two who turn my head the most are Adachi's desk neighbor, Kudou, and their introverted classmate, Midorikawa.
Kudou is a cheerful, friendly girl who, like Adachi, turns a blind eye to Yano's bullying. What strikes me about her as intriguing is that she has double teeth, and I point this out, not because I'm into girls with poor dental hygiene, but because she isn't bullied for it. She has enough charisma to get on and stay on people's good side, in spite of this physical deformity, and she in this regard acts as a foil to Yano, because you realize that if the bullied girl were more socially attuned, she likely wouldn't catch her classmates' ire.
The other girl I wanna mention is Midorikawa, a bibliophile who can't be arsed to mutter more than a “Mm” whenever somebody addresses her, but whenever she enters a scene, you'd think the princess of Denmark were arriving. Two things make her interesting. The first is that she's popular through no means of her own. It was Yano who turned her into an A-list celebrity overnight. The second is that she has the same <90° eyeballs Yano has. She has exactly one line in the book that isn't a noncommittal gurgle, and that's to tell the protagonist that his bosom buddy isn't the sweetheart he thinks he is.
Morsels like these are what make At Night, I Become an Aqrabuamelu a tantalizing read but ultimately an unsatisfying one. So many details and subplots are teased, but we only get the loosest resolution to what any of them are. As soon as Adachi's character arc is resolved, and I mean the second he changes as a character, the book decides it's put in a hard day's work and retires for the night, only to tragically pass from an undiagnosed heart condition.
It's wishful thinking, but I'd like to see a sequel to At Night, I Become an Erymanthian Boar. Adachi may not usher in sweeping reforms and change the classroom into an environment which accepts and welcomes oddball individuals like Yano, but the book has a unique identity, being just a slice of two weeks at school, not much different from any other two weeks at school. But since Adachi's character arc resolves, I'd like for Yano to pick up the narrator role so that we get to hear her thoughts and examine how the gears in her head crank. Maybe we'll also get to know if the nighttime guards are real or figments of her imagination, and if they are real, their standard of operation for taking down a Hecatoncheires like Adachi.