★Japanese Voice Actor: Kaolip
★Japanese Death Metal Voice: Rarecho
★English Voice Actor: Erica Mendez
★English Death Metal Voice: Jamison Boaz
★German Voice Actor: Julia Stoepel
★Spanish (LA) Voice Actor: Desiree González
★Spanish (EUR) Voice Actor: Vera Bosch
★French Voice Actor: Sophie Landresse
★Italian Voice Actor: Iolanda Granato
★Portuguese (BRZ) Voice Actor: Agatha Paulita
★Cantonese Voice Actor: Gu Yuxue (顾咏雪 / 顧咏雪)
Retsuko's appearance is based on a Red Panda. She has light orange fur on her face, black eyes, white ears, brown legs and arms, and a brown and light orange striped tail. Retsuko is seen in many different outfits throughout the series, but her typical clothing consists of a peach sweater with jewels around the collar and plaid skirt with black Mary Jane shoes. During the winter, Retsuko is usually seen wearing a navy blue peacoat, black skirt, tights and boots, and a peach scarf. Her work apparel is the typical female office uniform: blue vest and skirt, white dress shirt, and black shoes.
When she starts screaming death metal, Retsuko's appearance changes to KISS-like makeup, sharper teeth, a split tongue, and is often crying and her eyes glow the color blue. While screaming death metal as well, the kanji for rage (烈) appears on her forehead.
In her daily life, Retsuko is a demure, softly-spoken and polite young woman who works diligently, often being the only person to work overtime- usually because her bosses drop their work on her desk to leave on time. She is kind and a slightly rigid, although, when drunk, she loses all mental filters and speaks her mind.
Internally, however, Retsuko has a vicious temper, which she curbs by hiring a karaoke room and screaming her lungs out to death metal. She's a very talented singer in this respect, usually venting about her work, social, or romantic life.
★Resasuke: Retsuko and Resasuke briefly dated, but broke up after Retsuko realized that Resasuke didn't have the capacity to care about her the way she did for him. Resasuke was absentminded and not very attentive, but supportive of Retsuko nonetheless, especially after she revealed her true colours as a death metal singer. However, his response was underwhelming and clearly not appreciative of the meaning behind Retsuko's words, and, whilst he was kind, she realised that she couldn't continue the relationship with him.
★Gori and Washimi: Gori and Retsuko, along with Washimi, attend a yoga class together, as well as working at the same trading firm. Gori is a director in Sales, and Washimi is the secretary for the CEO of the company. Gori and Washimi help Retsuko come out of her shell a bit as a person, continually offering advice, support, and friendship. They were also the first people that Retsuko trusted with her death metal "secret".
★Puko: Retsuko's easygoing, free-spirited friend from high school, and drinking buddy. Puko invited Retsuko to join in on her international goods store, but Retsuko had to decline after finding that it would be based on internet sales and that her current, stable job was more wise. Despite this, Puko comments on how she admires Retsuko's responsibility, even going as far as to say that the reason she can be so carefree is because of hardworking people like Retsuko.
★Haida: One of Retsuko's coworkers, who cares for Retsuko deeply, although she apparently was unaware of this for quite some time. Fenneko acted as a third wheel, both in helping Haida come to terms with his feelings for Retsuko, and ensuring Retsuko didn't end up with anyone else.
★Fenneko: An accountant alongside Retsuko, Fenneko is cunning and intuitive, able to deduce much about her coworkers. She despises Tsunoda, and expressed extreme suspicion of Retsuko when Tsunoda posted a selfie of them both, but nonetheless cares for and is even protective over Retsuko (as shown when she attended the single's mixer as Retsuko's "bodyguard", quite literally ready to maul anyone who set their sights on her).
★"DEATH METAL IS MY SOUL!!"
★"GET YOUR DIRTY PAWS OFF MY MONEY!!"
★"CHOKE ON MY RAGE!!"
★"If I've learned anything, it's that life doesn't go the way you expect. There are surprises, good and bad, and sometimes you fall on your face. But even if it's awkward, even if it hurts, you keep moving forward because when you do, you're already a little bit stronger than yesterday."
★"If you don't say it for real, I can't give you an answer."