The female protagonist of Tonari no Kaibutsu-kun. As far as Shizuku is concerned, grades and studying are the only things that warrant her attention. She finds friends to be unnecessary and cannot find meaning in making connections with others. As a result, she acts indifferent and dismissive, earning her the nickname "dry ice" among her peers from an early age. After meeting the class delinquent Haru to deliver some class handouts, she is often put-off and at times horrified by his monstrous behavior. However, after seeing that he is actually well-meaning and kind under his extremely coarse behavior, she shows him kindness, and he responds by saying he is attracted to her. Despite herself, Shizuku finds that her perspective in life starts changing as she interacts with Haru, and she eventually becomes attracted to him as well. However, Shizuku and Haru never seem to be on the same page when it comes to their feelings, leading to an unbalanced romance between the two.
Berserk Button: Shizuku's studies are always her top priority, so she doesn't take kindly to them being interrupted or made light of.
Control Freak: A big part of Shizuku's character is her need for stability and control. As Shizuku's growing feelings for Haru start affecting her concentration in school, she starts avoiding him as she can't quite deal with her feelings and her schoolwork at the same time.
Cool Big Sis: Takaya views his sister in a favorable light and admires her, and for Shizuku's part, she tends to dote on him more than one would expect from her.
Deadpan Snarker: "Lately, Haru has been acting strange. Well, I guess that's nothing new."
Defrosting Ice Queen: Over the course of the story, Shizuku gradually finds that she enjoys hanging out with friends, and falls in love with Haru.
Emotionless Girl: Not being used to having friends to interact with, Shizuku is very emotionally withdrawn, and typically refrains from revealing her personal feelings or worries.
Friendless Background: Not that Shizuku herself actively sought out any friends. She felt more fulfillment from earning high marks than she did from spending time with her classmates.
Lack of Empathy: What earned her the nickname, "Dry Ice". When she was little, she didn't care about the class pet dying. Instead, she asked about the next assignment. Now she's learning to be more careful with other people's emotions.
Loner-Turned-Friend: Shizuku starts off seeing others as mere interactions that mean nothing, to eventually acknowledging she has friends.
Loony Friends Improve Your Personality: It can be argued that Haru's (and Natsume's) influence helped her to open up to others, and when she steps back to observe this, she does seem to think that she is changing for the better.
Missing Mom: Not so much missing as absent because she's constantly working. Shizuku gets calls at regular intervals from her mother, though her mother can also be insensitive and forget from time to time. Takaya hints that Shizuku is more disappointed by this than she lets on.
Morality Chain: Shizuku's very presence is enough to get Haru to calm down and behave. If she's not around, Haru can relapse into his old, violent ways. The chain Haru is often see wearing in official media is a representation of this relationship.
Serious Business: No, she's not messing around. For Shizuku, love is of debatable importance compared to studying.
Straight Man: Shizuku plays this to nearly every other character due to them all having varying quirks. The only ones who are probably just as or perhaps even more level than she is are Sasayan and Micchan.
The Stoic: Downplayed as the story goes on, but she generally is well in-control of her reactions and emotions. This is why interacting with Haru ends up shaking her as much as it does; as she grows closer to him, her feelings are not as easily kept in check.
Sugar and Ice Personality: Shizuku generally does not enjoy interacting with others, but she shows glimpses of her sweet side to Haru.
Tranquil Fury: When she's at her angriest, she tends to just be silent and glare at the target of her anger.
Tsurime Eyes: Her eyes are almost always serious and focused.
Well Done Daughter Girl: A case can be made that she is this to her mother. While her mother is proud of Shizuku and happy that she works hard, she is also distant from Shizuku and places her work as a top priority, leaving Shizuku disappointed when her mother is unable to show up for family events. Since Shizuku modeled herself and her work ethic after her mother, it may be that her mother's distance from her family also led Shizuku to create a similar dissociation from her peers.
The male protagonist of Tonari no Kaibutsu-kun. Stubborn, violent, and impulsive, Haru is the titular "monster" of Tonari no Kaibutsu-kun. Being suspended at the beginning of the school year, Shizuku delivers his class handouts and though he faces expulsion, he refuses to return to school up until he makes an emotional connection with Shizuku, at which point he declares that he likes her and begins attending school just so that he can spend more time with her. Going from one extreme to the next, he can be very troublesome and frightening to deal with, usually making threats and getting into fist fights with others. However, he has good intentions and wishes to connect with others, though he can be possessive of those he is close with, especially Shizuku, due to a lack of stability in his own personal life.
Ambiguous Innocence: Haru's extreme innocence can occasionally cross over from adorable into disturbing.
Because You Were Nice to Me: Haru initially grows attached Shizuku because she stood up for him when his friends were treating him poorly and encouraged him to look forward to the time when he'd be surrounded by true friends. However, his situation actually leads to an obsession with Shizuku rather than truly liking her, and it takes time for him to develop real romantic feelings towards her.
Bishounen: If not for his habit of glaring, Haru is actually very handsome.
Brilliant, but Lazy: Shizuku has stated several times that Haru is actually far smarter than she is, but he doesn't apply himself.
Chick Magnet: After he stops glaring at everyone all the time once Shizuku tells him that he should try smiling more. He ruins it though by going on an assault against a few bullies, leading the majority of the school to go back to fearing him, though this fear dies down after a while as he starts mellowing out.
Cloudcuckoolander: Haru tends to come off as this, because of his lack of experience in normal social interaction.
Crazy Jealous Guy: For Shizuku, especially when it comes to Yamaken. He even passingly mentions that while he can't break Shizuku's legs to keep her from running away from him, he would gladly do so to Yamaken.
Dark and Troubled Past: Haru is a product of his family history, so at the beginning of the story, he is very socially awkward and emotionally stunted, putting it lightly.
Delinquent: His habit of settling problems with violence and refusing to attend school has firmly planted Haru in delinquent territory.
Hair-Trigger Temper: A serious problem for Haru starting out. As the story goes on, he has to work on controlling his anger and not acting completely on his emotions.
Hot-Blooded: Although he usually seems detached and aloof, he can quickly become riled up if something ticks him off.
I Just Want to Have Friends: Haru's lonely 3 years of middle school taught him that life is an empty experience unless you have people to share it with.
Intelligence Equals Isolation: A strangely averted case; Haru is intelligent because of his isolation. While Haru didn't attend any of his classes in middle school, he read about a lot of advanced subjects in his spare time and is thus far ahead of the rest of his classmates. This is in part due to the fact that he lived with his aunt, who was a professor at a university.
Yandere: In Haru's scariest moments, he shows flashes of this.
Voiced by: Atsumi Tanezaki
A girl who is in the same class as Haru and Shizuku. Self-proclaimed to be "hopelessly stupid" at her schoolwork, she begs Haru and Shizuku to tutor her for her retest, luring Haru with an invitation to a social meetup with her online friends. Though Haru's attempts at tutoring her fall short, Shizuku's more direct explanations and concise outlines help her pass, and she remains friends with the both of them from then afterward. As she is very attractive and receives many love confessions that she always rejects, she was bullied and ostracized by both her male and female classmates. Thus Asako wants nothing more than to make lots of female friends while having nothing to do with the opposite sex. As she had trouble making friends in real life, Asako turned to online blogging and often retreats to her site as a means to be popular and escape her real life troubles.
Book Dumb: Her grades are absolutely awful, but she really does try her best.
Brainless Beauty: A surprisingly positively portrayed example. Asako is definitely not the sharpest tool in the shed, and she's constantly shown to have to take retests, but she dislikes her popularity with males and in spite of being Book Dumb, she cares very much for her relationships with her friends.
Cloud Cuckoolander: Though probably milder than most cases and definitely not as strange as Haru, Asako is still weird and can get a bit creepy sometimes. Shizuku once caught a glimpse of her typing a message on her blog that she still needed a couple of strands of Shizuku's hair in order to perform a ritual that would ensure they'd be best friends forever.
Dude Magnet: She's very cute, and boys apparently flock to her constantly.
Does Not Like Men: Asako has an aversion to men due to countless guys asking her out. This unfortunately leads to girls disliking her because she's popular with guys, and guys disliking her because she rejects them.
Early-Bird Cameo: She was among the group of students when Haru stripped for gym. To be more precise, she was behind Shizuku on her right.
Shipper on Deck: Asako for Haru and Shizuku. She gets very upset when Sasayan questions how sincere Haru's feelings for Shizuku are.
Unwanted Harem: The three guys who tend to follow Yamaken around are always ogling her, and she's never too thrilled about it.
With Friends Like These...: Her old middle school friends. When Natsume started hanging out with one of her friends' crush, people started talking behind her back. Nothing explicit is stated, but it's possible that they thought she fooled around with other guys. When they see her years later, they continue to make comments about her, which makes her start crying.
A classmate of Shizuku and Haru. Souhei "Sasayan" Sasahara first approaches Shizuku while she was studying alone in the library during his baseball team's practice. As he went to the same middle school as Haru, he's interested in how Shizuku somehow "tamed" him, since he never showed up for any of his classes in his old school. Sasayan eventually becomes incorporated into the main group's social circle after helping build a chicken coop for the class's pet chicken along with the others. Friendly and laid-back, Sasayan is the most socially aware and is popular among his peers. Though not quite Wise Beyond His Years, he is much more perceptive of the others' interactions and as a result is very good at concealing his own feelings from others.
One of Haru's former "friends". He used to go to school with Haru and picked on him for being smarter than him. By time the story gets going, he and his friends are hanging out with Haru and are taking advantage of his friendless situation. However, Shizuku calls them out on this and Haru leaves them to hang out with her. Months after the confrontation, he and Shizuku meet up in cram school, which gives him a chance to flirt with her. Initially, these were attempts to provoke Haru, but he eventually does start falling in love with her.
Deadpan Snarker: His comments are typically blunt, matter-of-fact one-liners.
Evil Blonde: Subverted. He starts off by using poor friendless Haru, but leaves him alone after Shizuku tells him off. Then he starts flirting with her just to make Haru mad. However, he develops feelings for Shizuku and eventually softens up a bit.
The Gadfly: Yamaken seems to enjoy messing around and pushing his friends' buttons to see how they respond.
Jerk with a Heart of Gold: Yamaken surprisingly turns out to be this as well, initially debuting as a gang leader but turning out to be rich, intelligent, and has a habit of looking after Shizuku.
Love Confession: He attempts this for Shizuku in the OVA. However, Shizuku headbutts him before he completes it.
No Sense of Direction: He managed to get lost repeatedly at Shizuku's school, again and again finding himself rummaging in the bushes.
The Rival: Surprisingly, in both the romantic and the intelligent department. He is incredibly smart, but not as smart as Haru, though. He has feelings for Shizuku, initially for the wrong reason, but Shizuku has feelings for Haru instead. In one episode, they get in a fight because of their jealousy of the other person.
A classmate of Haru and Shizuku's and class president. She's very shy and rarely interacts with other people outside of the main cast. She does have one friend affectionately called "Yuu-chan" who she regularly talks to.
Cool Big Bro: Often gives helpful advice to Haru and Natsume.
Oblivious to Love: Up until her confession, Mitsuyoshi had no idea that Natsume had feelings for him.
Cool Shades: It's revealed that since his eyes are similar to his uncle's (Haru and Yuuzan's father), he wears them as a cover.
May-December Romance: Subverted. When Nastume confessed her love for him, he rejected her. It wasn't because he didn't like her, but it was because he was in his twenties and she was still in high school.
Haru's estranged older brother. He often comes by Mitsuyoshi's apartment to visit Haru, but he's unable to talk to him since Haru is terrified of him. Occasionally, he runs into Shizuku, either by sheer coincidence or pure intent, and uses her as a means to talk to Haru.