A group of plaintiffs have filed a lawsuit in Tokyo's district court against Coincheck, the cryptocurrency exchange where hackers stole more than US$650 Million in NEM coins last month.

The case could be one of Japan's biggest consumer rights in many decades.

In order to get a handle on the hack, Coincheck had to freeze customers' accounts, prevent customers from making withdrawals.  The plaintiffs are five individuals and two companies from the greater Tokyo area who are demanding Coincheck return frozen assets worth AU$237,000.  They want it paid in one of the dozen cryptocurrencies Coincheck handles - including NEM, Ripple, and Bitcoin - rather than regular cash.

"We also would like to expose how cryptocurrencies were managed (by Coincheck) through this lawsuit," said lead lawyer Kanehito Kita.

The plaintiffs' attorneys plan to file a second suit by the end of the month that will seek to recoup the decreased value of cryptocurrencies that has been triggered by the debacle.  They say around 1,000 Coincheck customers have expressed interest in signing on the class-action.