The 17-year-old student says she was beaten by boys with broom sticks, slapped in the girls' bathroom, and even attacked during a swimming lesson.
"I was the last one to get out of the pool," she said. "A brush flew out of nowhere and it hit me underwater. I nearly drowned. I had a huge bump on my forehead."
Nanae started skipping school, and even thought about taking her own life.
She's not alone.
More Japanese school pupils commit suicide on September 1 each year than on any other date, according to figures collated by Japan's suicide prevention office over a period of more than 40 years.
The grim spike in the statistics is linked to the typical start date of the new school term after the summer holiday has ended.
"The long break from school enables you to stay at home, so it's heaven for those who are bullied," Nanae said. "When summer ends, you have to go back. And once you start worrying about getting bullied, committing suicide might be possible."
Japan has one of the highest rates of suicide in the world, and it is the leading cause of death among those aged 15-39. The government's figures show that in total 18,048 under-18s took their own lives between 1972 and 2013.
Nanae said she became a target for bullies after she transferred schools for a short time before returning -- meaning she was branded as a truant.
When the bullying worsened, she considered suicide, but did not go through with it.
"I thought that actions such as cutting my wrist would cause trouble for my parents, and committing suicide would not solve anything."
In the end, Nanae decided to stop going to school and stayed at home for nearly a year.
Nanae's mother, Mina Munemasa, was supportive of her daughter's decision.
"Nanae was saying things like, 'If I jump off the Tokyo Tower, I think I can fly," Mina said. "I don't think school is a place where you have to risk your life to go."
Nanae thinks the Japanese education system's focus on collective thinking is at the root cause of the problem.
"In Japan, you have to fall in line with other people. And if you cannot do that, you're either ignored or bullied," she said. "You are required to have a unified opinion, and it crushes the uniqueness every person has. But that uniqueness is not something to destroy."
Some experts agree. Child psychiatrist Dr. Ken Takaoka said the suicide rate increases when school restarts because schools "prioritize collective (action). Children who do not get along in a group will suffer."
To raise awareness of the issue, a Japanese non-profit organization, Futoko Shimbun, is even printing a newspaper for children who stay home to avoid bullying. Keiko Okuchi, one of the organization's representatives, said the problem is exacerbated by a culture that dictates that going to school is the only option.
"It is a living hell for children who know that they'll be bullied at school, yet they have no other choice but to go," she said.
Now, Nanae has returned to her studies and is also singing in a pop band called Nanakato along with her brother. Nanae hopes that one day they will have enough fans to fill Tokyo's famous arena Budokan, and play their music in a foreign country.
Nanae is also trying to help others being bullied by writing a blog about what she went through.
"It would be great if (the blog) helps at least one person stop thinking about committing suicide," she said.
Nanae's mother said her daughter's time on the Internet was a key factor in helping her get through the bullying.
"By creating connections with people in Japan as well as other countries, she was able to regain her confidence," Mina said.
"Adults tend to say that the Internet is dangerous but there are definitely some children who are saved by it."
If you have had thoughts of suicide, please seek help: National Suicide Prevention Lifeline
, 1 (800) 273-8255.