Tokyo (CNN) A 38-year-old Japanese national has filed a lawsuit against his employer for alleged harassment after taking paternity leave, in a landmark case that looks set to challenge Japan's often highly-gendered corporate culture.

Japanese law grants both men and women up to one year of leave from work after having a child. Parents are not guaranteed pay from their employer, but are eligible for government benefits while off. However, only 5% of eligible fathers took paternity leave in 2017, according to government data

The case, which appeared before a Tokyo court on Thursday, was brought about after the man claimed that his employer, sportswear maker Asics, purposefully sidelined him from his job in sales and marketing following his return from parental leave in 2015 and 2018. Asics has denied the allegations.

The case is among the first to tackle the issue of paternity harassment in Japan, where working culture often dictates that male employees work long hours and place company loyalty ahead of the family.

The man, who has requested anonymity due to the sensitive nature of his claim -- media in japan have honored the request -- took six weeks off after his first son was born in 2015 and then another 13 months of leave before his son's second birthday. Asics offers male employees up to two years paternity leave.

"This was a natural choice for me," he told CNN. "I wanted to to take care of my newborn and witness his growth. I also wanted to protect my wife from the baby blues."

The man claims that on his return to work he was transferred to a subsidiary company's warehouse and tasked with manual jobs, which he alleges resulted in an injury to his shoulder. He was then transferred to an office job.

"I was assigned to carry out research on disabled people's rights in the workplace and to translate company rules into English, two areas I have no experience or expertise in," he said. "I spend all day staring at my computer with not much to do."

Following the birth of his second son in 2018, he took a second parental leave lasting for 13 months. On return to work he claims the situation has continued and feels as if he is being pushed out.

The man wants his original role back and 4.4 million yen (US$41,000) in damages, according to his lawyer Naoto Sasayama. "The job he was transferred to was not the one he was hired for and this is very clear harassment against taking his paternity leave," said Sasayama.

Asics has refuted the man's allegations. "We have been negotiating sincerely with the legal representative of the employee as well as with several labor unions he belonged to," said the company in a statement. "We find it regrettable that we have not reached a final solution and we look forward to clarifying the facts in court."

According to Asics diversity policy, it is committed to meeting a government set goal of 13% paternity leave among eligible fathers. Currently, 8% of Asics' male employees take the leave they are entitled to

'Constant harassment'

The case is among a number of similar disputes currently underway.

Glen Wood, a Canadian who has been living in Japan for around 30 years, was working as a brokerage manager at Mitsubishi UFJ Morgan Stanley in the Fall of 2015 when his son was born six weeks premature. "My partner was working in Nepal at the time so he was born there and doctors told us they weren't sure he would make it," Wood told CNN.

He asked his employer for time off, as part of his paternity leave, but he claims he was denied.

"I was told I wasn't eligible because my family didn't have a maternity booklet, which is an official record of a pregnant woman's medical data," said Wood.

Despite the ruling, Wood decided to leave anyway. "My son was in a life or death situation and I needed to be by his side to get him a Canadian passport, a precondition to bring him back to Japan."

But on his return to his job five months later, in March 2016, Wood claims he was subjected to constant harassment. The company has denied the allegations.

Glen Wood, a Canadian citizen living in japan, is suing his employer for harassment. He says he was punished for taking the paternity leave he was entitled to.

"My responsibilities were cut by about 95%, with only secretarial work left for me to do. I wasn't told about meetings or given the wrong times and then criticized for not attending them. My emails and phone calls were left unanswered," said Woods.

He claims he was also asked to take a paternity DNA test, even though Japanese law provides leave for parents of adopted children and despite the fact he was the father of the child. He claims he was also forced to undergo two psychiatric evaluations.

In 2017, he decided to sue his employer and in 2018 was fired. Court proceedings are due to begin on October.

"I am asking for my job back," said Wood. "I really loved my work and career and don't want to have to give it up."

In a statement provided to CNN, Mitsubishi UFJ Morgan Stanley denied that Wood was harassed. The company said it has submitted its evidence to the court through its lawyers and would refrain from commenting further as the case is ongoing.

Wood is now hoping his court case will set a precedent for other alleged harassment victims. "In Japan, it is considered almost treasonous to take time off from work, even if you are incredibly sick, have a dying relative or have just had a baby," said Wood.

petition on Change.org supporting Wood and calling for "Zero-tolerance for Workplace Harassment in Japan!" had garnered over 3,800 signatures on Thursday.

"Most of my colleagues were very supportive, even if they couldn't take my side publicly for fear of losing their jobs," said Wood.