Media playback is unsupported on your device Media caption A heavy metal-loving panda full of rage is a new character Japanese working women can identify with

Being kawaii - or cute - is a huge part of being a good Japanese girl, but what happens when you finally grow up? For decades Hello Kitty was Japan's ambassador of cute, but now an angry red panda is channelling the frustrations of ordinary working women.

In Japan, girls are taught etiquette from a young age and often much more strictly than boys. It's not just about your appearance, but also how you behave.

The Japanese firm most closely associated with kawaii products, Sanrio, understands this all too well.

It can take credit for the global phenomenon that is Hello Kitty, the well-mannered kitten which Sanrio claims is actually a British schoolgirl, despite being seen as perhaps the most quintessentially Japanese thing ever. She even appears in educational videos to teach children about manners.

But recently the company has introduced a character with a somewhat different approach to life.

Aggressive Retsuko - or Aggretsuko - is a 25-year-old red panda who works a mundane office job.

Image copyright Sanrio Image caption Aggretsuko is far from the cute Hello Kitty stereotype Sanrio is also responsible for

Her appearance is cute, but when she gets angry at her boss or colleagues her face transforms until it becomes a made-up mask somewhat reminiscent of American glam metal band Kiss.

"I'll quit one day anyway!!! This is not my fate!!!" she screams inside, as her boss piles up more paperwork on her desk.

After work, she goes to karaoke alone and sings metal songs with lyrics complaining about her day.

"She reminds me of myself when I was 25," said Reika Kataoka who is now a stay-at-home mother. "I used to spew venom like that at work."

Image copyright Sanrio Image caption Aggretsuko hates her job

"Japanese girls suffer from a social structure where we are supposed to act properly," a cross-dressing singer who goes by the stage name Charlie Shikazaki and works as a researcher by day, told the BBC.

"But many of us have two sides. They might look cute on the outside but can be aggressive inside. Sanrio shows this kind of girls quite well with Aggretsuko," she explained.

In a society which puts a lot of value on politeness, you don't often see people expressing raw emotions in public and the Japanese language doesn't have equivalents to the everyday profanities you might hear muttered at work in English.

Image copyright Sanrio Image caption She spends much of her time on the edge of rage

'Heartfelt screams' of office workers

So how was Aggretsuko created? It was in fact through a popular vote of characters submitted by Sanrio staff and others. The theme was "salaryman" or office workers. It clearly struck a chord.

Sanrio says the designer, who goes by the name of Yeti, wants to remain anonymous. But through the company's corporate communications department, the designer said: "I observed office workers who are at the centre of Japan's corporate culture and I could hear their heartfelt screams."

"Japan's working environment often becomes an issue and I think there are many people who are enduring a lot of stress," Yeti added.

It is a subject being debated in Japan at the moment as just last month, the chairman of Japan's top advertising agency Dentsu resigned to take responsibility for the death of a 24-year-old employee. Matsuri Takahashi who took her own life on Christmas Day in 2015, after complaining about excessive working hours.

Her death is part of a phenomenon known as karoshi, or "death from overwork", which was first recognised 30 years ago.

When we asked Japanese women what their Aggretsuko moment is, their most uncute habits, they were certainly forthcoming.

Image copyright Charlie Shikazaki Image caption Singer Charlie Shikazaki says she got tired of the pressure to seem feminine

Ms Shikazaki said it was the pressure to look cute and behave appropriately that drove her to start singing in a band dressed as a man one year ago. It was "to express my feelings and emotions".

"Because I used to teach at universities, the reaction from my former students has been overwhelming - like 'what on earth happened?'," she said.

"I sing in both London and Tokyo but I find that people in London accept me without any hesitation."

"But in Japan, I don't really expect them to understand so I haven't told many people who I used to work with," she added.

Image copyright Sanrio Image caption Aggretsuko drowns her sorrows with beer and heavy metal - most unladylike

For communications specialist Momo Ohmura, it is about what she eats and drinks. "People say what I order at restaurants isn't cute," she said. "I like things like dried fish and inner organs like chicken liver. I also love Japanese sake - even more than champagne!"

Kawaii ladies are allowed to drink in Japanese society, but being able to drink more than men is not something you'd show off to your boyfriend.

Many Aggretsuko fans were surprised to find out that she was created by Sanrio.

Image copyright Sanrio

But she is not their first unconventional character.

Gudetama or "lazy egg" was born in 2013 and suffers from crippling depression, spewing cold one-liners that reflect the dark realities of life.

The character was seen as reflective of the younger generation's diminishing self-esteem and growing unhappiness.

Image copyright Sanrio Image caption The character is occasionally cheerful, and even recently found love

"I always thought Sanrio's target audience was children but I wonder if they are targeting millennial or older people," said Ms Kataoka.

Ahead of Valentine's Day, Aggretsuko appears to have fallen in love. In her weekly programme on broadcaster TBS, for once, she didn't get angry for an entire episode.

While it is adorable to watch her being just cute, her many fans hope she will continue to vent her darker feelings even after finding the love of her life.

This appears to be what more working women in Japan want licence to do.