TOKYO - A bitter feud is tearing one of Japan's wealthiest families apart, with tit-for-tat lawsuits filed as accusations of blatant racism fly.

Mr Han Chang-woo, 89, founder and chairman of Maruhan, a leading operator of pachinko (slot machine) parlours across Japan, has sued Ms Marina Haba, 51, the eldest of his six children for the return of a loan of 480 million yen (S$6.2 million), with interest.

Ms Haba, who continues to go by the name of her first husband with whom she has two children, has remarried to Mr Joe Wallace, an African-American man. She says her father frowns upon the relationship.

"My father did not approve of my relationship with Joe. He never has," Ms Haba says in court documents seen last week by The Sunday Times. "My father has made it plain that he does not approve of my relationship with a black man."

Mr Han reportedly denies the allegations, and Maruhan's corporate social responsibility pledge says the company is committed to diversity and inclusion.

Mr Han is a self-made entrepreneur born in South Korea when it was under occupation by the Japanese.

He migrated to Japan when he was 16, graduating with an economics degree at Hosei University, eventually founding the Kyoto-based Maruhan in 1957 and becoming a naturalised Japanese citizen.

The company is a leading player in Japan's US$200 billion (S$270 billion) pachinko industry, but has diversified into businesses spanning bowling alleys, golf courses and cinemas. Its investment arm is based in Singapore.

The company's success has made Mr Han the country's 19th wealthiest man, according to the Japan's 50 Richest list compiled by Forbes this year. His net worth is estimated at US$3.8 billion.

The tycoon gave all six of his children 1.5 million shares each in the company many years ago, effectively making each of them multi-millionaires.

While her four brothers now hold top positions in Maruhan, Ms Haba also stood to benefit from the generosity. She says in her court documents that she has been living a comfortable life from income reaped from company dividends.

But this steady stream of income was abruptly cut off, she claims, due to her father's disapproval of her relationship with Mr Wallace, 55.

They first met in 1991 when Ms Haba was a college student and Mr Wallace a professional basketball player in Japan.

They split up after Mr Wallace retired from the sport in 1994 and became a marketing executive.

Each of them would form their own families. But they both divorced their partners in their respective marriages, reconnected via Facebook in 2011 and eventually wed in 2014.

Mr Han has never met Mr Wallace, Ms Haba says in her court documents, and contends that her father's racially-motivated campaign to pressure her into making a choice between her husband and her livelihood violates her rights.

She intends to sue her father in the Kyoto District Court for the rightful return of her stock dividends worth an estimated US$300 million, as well as to reinstate her stock options.

As a first step, she has filed a court order in the United States territory of Guam, where Maruhan runs a subsidiary office, to force the company to produce documents that she needs to build her case.

She has engaged an international team of lawyers in Tokyo, Los Angeles and Guam, including from major law firm Morrison & Foerster.

This strategy is borne from the formidable hurdles she would face in Japan, where civil courts are typically friendly towards defendants.

"The type of discovery Ms Haba seeks is common in American courts, but unavailable in Japan," her attorneys wrote in court documents to the court in Guam.

"The requested relief is for the purpose of obtaining limited, but necessary, discovery in connection with a pending and anticipated civil proceeding before the Kyoto District Court."

They cited a US law that provides a mechanism for parties to undertake discovery through a US court to obtain information that is relevant to a foreign civil case.

If she succeeds, her case will potentially open the doors for document discovery in future civil lawsuits in Japan against companies or individuals with connections to the US.

"I was forced to hire counsel to try to correct the situation," Ms Haba says in her court documents. "It was extremely painful that my father, who I have always loved and shown the greatest respect, would take this action against me in an effort to bring me under his control and to try to force me to leave my husband."

Her father had filed two lawsuits at the Kyoto District Court, dated October 15 last year and March 24 this year, for the immediate return - with interest - of the 480 million yen loan.

Ms Haba says in court documents that Mr Han had granted her the personal loan on September 2 last year after she returned to Kyoto under financial duress to meet her estranged father to discuss her financial situation.

But she claims that the loan was made only under such conditions that she leaves Mr Wallace and hands over her passport to her father so that she can only leave Japan with his permission, among other terms.

She says that she agreed out of financial desperation, according to the court filings, but this was meant only as a ruse that she and Mr Wallace had never planned to follow through.

She could have underestimated how wide and deep Mr Han's network runs, however, given that they were found out barely a month later when they were spotted on the streets of Tokyo.

Mr Han allegedly flew into a rage, prompting the lawsuits demanding the immediate return of the loan and, Ms Haba says, the seizure of her property, bank accounts and the withholding of her stock options.

Her lawyers argue that this was "clearly done at Mr Han's direction to eliminate Ms Haba's sole source of financial independence, to impose his dominion and control over Ms Haba, and to force her to accede to his demands".

A multi-continental love story hits resistance

Ms Marina Haba, the eldest of six children to Japanese pachinko slot machine mogul Han Chang-woo, first fell in love with Mr Joe Wallace, a strapping basketball player, when she was a college student in 1991.

He was then playing professional basketball in Japan for Isuzu Motors Gigacats.

Although they were dating for less than a year, Ms Haba uprooted her life and followed Mr Wallace's basketball career by moving to Spain, Argentina and Paris but they parted ways after his professional retirement.

Mr Wallace, born in California, returned to the United States while Ms Haba returned to Japan. They lost contact for 15 years, during which time they got married, had children, and divorced from their partners.

They reconnected via Facebook in 2011 and, after a meeting in Vancouver, rekindled their romance and married in 2014.

Ms Haba is now alleging that her father is racist, with his disapproval of her relationship with an African-American man the reason why he cut her loose.

Mr Han is suing her for the immediate return of a loan of 480 million yen (S$6.2 million) with interest that he granted her in September last year. He has also taken legal steps to seize all her assets and block her bank accounts.

But Ms Haba claims that her father and his company Maruhan had unjustly withheld her rightful stock options and dividend payments, and intends to counter-sue in the Kyoto court.

But as a first step, she has launched court proceedings in the United States territory of Guam - where Maruhan has a subsidiary - to facilitate the document discovery process to build her case in Japan.

"As leverage to force his daughter to divorce (her husband), Mr Han has moved to reclaim her shares in the family business ... that he long ago gave to his daughter without condition," say her lawyers.