|“||It is impossible to not hurt someone. Humans unconsciously hurt others by simply existing. Whether you are alive or dead, you keep hurting people. Getting involved will hurt them, but trying not to get involved might hurt them too. But if it's someone you don't care about, you won't notice you've hurt them. What's important is your awareness of it. It's because you care about them, that you feel like you've hurt them. Caring about someone means being resolved to the fact that you'll hurt them. The more people care for each other, the farther out of reach certain things get. But that's not something to be sad about, I think it's probably something to be proud of.||”|
—Shizuka Hiratsuka, My Teen Romantic Comedy SNAFU, TOO!
Shizuka is a fairly tall and busty young woman with long, black hair that reaches her shins, sticks out at her neck and falls over her shoulders and purple eyes. She is seen wearing a knee length white jacket similar to a lab coat, a black vest, and black pants with a brown belt. Underneath her vest is a dress shirt and a loosely worn short tie.
In the light novels, she wears a longer black tie and a grey belt.
Shizuka is an incredibly kind, friendly and responsible teacher who is open minded and believes in the future of her students. Pointed out by Yukino Yukinoshita, Shizuka wishes and works hard for the welfare of all her students. She cares about all the students which is perhaps best demonstrated when she becomes concerned about her student Saki Kawasaki regarding her late night job.
Despite her age, Shizuka enjoys reading shōnen manga to the extent that she often quotes or copies scenes from them, for example, when she proposes the battle royale contest between Yukino and Hachiman Hikigaya. She also enjoys having fun with her students and observing their interactions, further demonstrating her youthful outlook.
On her days off, she drinks until morning and sleeps till noon. She usually gets assigned in charge of various school activities like cultural festival, athletic festival, the article of Love Marriage, Chiba Wedding, and Christmas collaboration event, etc. was pushed onto her by the top management. Shizuka believes her "young" age is the main reason why she keeps receiving those assignments.
Although she is young at heart, Hiratsuka is very aware and sensitive about her age and single status. She is quite worried her prospects of getting married now that she is a late Christmas cake. (In Japan, there is a popular belief that women over 25 are too old for marriage. As people want to eat a Christmas cake no later than the 25th, so women want to get married no older than 25). When her age and marital status are brought up, she becomes visibly agitated, either becoming incredibly violent as she does with Hachiman, or sad to the point of crying in front of her students.
Observed by the e-mails she repeatedly sent to Hachiman, she is probably very insecure and even maybe has a Yandere side. She also shows her crafty side by tricking Hachiman into going to the Chiba village camp. She often shows her motherly, or care taking side.
She is quite wise and hands out advice when needed. She is always ready to give advice and counseling to her students. She sometimes forces the students to take part in activities for their well-being. An example of this is forcing Hachiman to participate in the Service Club, Chiba Village summer camp, and as a Cultural committee representative.
In the light novel she is said to be excellent in martial arts. It is hinted at in the anime by her displays of force towards Hachiman. Her skull clutch is described as an iron hold by Hachiman.
In accordance to her profession, she is also an excellent teacher and adviser, which is seen throughout the series. She can also play the bass which is shown in episode 12. It was mentioned that Haruno dragged her in a concert in the past.
- "Don't think you can graduate in three years!"
- "Didn't anyone ever teach you not to bring up a woman's age?"
- "Helping someone out is not a justifiable reason for you to get hurt"
- "That holds true even if you`re used to pain, There are people who`d be hurt by watching you get hurt"
- "If you stick to your way You won't be able to help someone when you most want to"
- "If you can't solve this in one word, then use all the words you need. If you can't trust words to get the job done, then you can pair them up with actions. You can use any words and any actions that you like. Let each of them be a dot to connect until you managed to form your answer. Shizuka to Hachiman 
- The name Shizuka (静) means "quiet".
- Shizuka's surname Hiratsuka means "flat" (平) (hira) and "mound" (塚) (tsuka).
- Shizuka loves ramen.
- Shizuka was the Point of character for Track 2 of drama bonus C.D titled Tatoeba Konna Birthday Song (たとえばこんなバースデーソング, "Birthday Song for you") of Volume 3.
- Shizuka's hobbies are reading manga and Harlequin Books, as well as motorbike riding and watching anime.
- Shizuka's spends her days off mostly drinking and sleeping.
- Shizuka is a heavy smoker and is often seen smoking Seven Stars cigarettes.
- It was shown on the opening and on Episode 8 of Season 2 that Shizuka owns a Red 2005 Aston Martin V8 Vantage. When Hachiman Hikigaya asks about her former car, she said that she just rented it (The rented car that Shizuka refers to is a black van that was shown during their trip to Chiba summer camp in Season 1 Episode 7).