Yoshikazu Kudo (not his real name) and his wife have both been deaf from birth. For decades they have lived at ease in an old but neat house built by Kudo's brother in Musashino, Tokyo. But things changed after the husband of Kudo's late sister disappeared, leaving behind over 80 million yen in debts.

Yoshikazu Kudo stages a protest outside of Dai-Ichi Kangyo Bank.

In 1997, Dai-Ichi Kangyo Bank and Sanwa Bank filed lawsuits with the Tokyo District Court to enforce contracts that made Kudo responsible for up 20 million yen of his brother-in-law's debts and secured his house and land as collateral.

Using sign language Kudo, 75, said he did not even know he had signed contracts making him the guarantor of his brother-in-law's loans until he received a letter from the court and another sister explained the situation to him in sign language.

The court has so far learned that bankers and the brother-in-law visited Kudo in his backyard in 1993 and 1994 and within 10 to 20 minutes got him to place his signature and personal seal on contracts.

Bankers claimed Kudo appeared to have understood the contracts after his brother-in-law gestured an explanation, although they admitted they didn't know exactly what the man told him. The brother-in-law, who borrowed money from the banks to cover his business expenses, had never learned sign language, according to his acquaintances.

Kudo's reading ability is limited as he did not attend school until the age of 11, when he started going to a school for the deaf in Tokyo's Setagaya Ward.

Kudo said he did just as his brother-in-law directed because the man was married to his sister, who had done a lot for him.

According to Les Deuel, a friend of the Kudos for over 17 years, Kudo "does not even understand the concept of a mortgage."

Deuel is one of a group of people trying to save the couple's house from seizure by the banks.

On the day of one of the bank's shareholders' meeting, the Kudos and their supporters were handing out flyers to the men in dark suits gathering outside its headquarter building in Tokyo's Chiyoda Ward.

"This is like a whole town," Deuel said, looking up at the large building. "I can't believe such a big company is taking this old man's house."

As disputes over consumer financial contracts rise, an increasing number of socially vulnerable people with little understanding of such matters are falling victim.

In January, the Kobe District Court dismissed lawsuits filed by Nichiei Co., a nonbank moneylender notorious for its strong-arm debt-collection methods, seeking repayment of a debt from a guarantor who also has a hearing disability and low literacy level.

According to the Japan Consumer Information Center, consumer complaints have nearly tripled over the last decade. Those filed by people who have signed contracts without fully understanding their obligations under them rose to 3,186 across the nation last year.

The center especially noted a significant rise in consumer complaints among the elderly and people with physical disabilities, officials said.

"Such cases include blind and hearing-impaired people who suffered huge losses in stock trading because they were not given enough information," said Ayako Shimizu of the center.

Disputes regarding asset management-related contracts entered under poor judgment also accounted for a majority of the consultations offered by Step, a Tokyo Metropolitan Government-affiliated organization for protecting the rights of the mentally disabled and elderly.

Toshio Aoyama, vice director of Step, said troubles are increasing partly because contracts in general are becoming more complicated as new products in such areas as finance and telecommunications debut in the market.

Lawyer Tesuro Taguchi, who represents Kudo, noted that the increased presence and social participation of the "weaker elements of society" may be another factor contributing to the rise in contract disputes.

"Bankers never thought of having people with disabilities sign as debt guarantors in the past," he said.

Taguchi said the court should clearly rule in Kudo's case that the banks bear the responsibility of providing an interpreter of sign language so hearing impaired people fully understand their responsibilities as contract guarantors.

Although he wants the court to rule in this manner, Taguchi said he hopes Kudo's case in any event helps to educate others.

To this end, members supporting Kudo's case performed a play about Kudo at a gathering of hearing impaired people in late May.

"Although you all have difficulty hearing, you are also required to make independent decisions," said Masao Ito, the organizer of the gathering, who is also deaf.