One of Japans largest lenders, Mizuho Bank Ltd, has became ensnared in the U.S. legal fallout from the collapse Mt. Gox, the leading bitcoin exchange that lost more than $400 million of customers digital currency. Mizuho held non-bitcoin currency on behalf of Tokyo-based Mt. Gox and its customers, according to the amended complaint by Gregory Greene, an Illinois resident who has said he lost $25,000 when Mt. Gox shut down last month. Canadian bitcoin traders filed a class action against Mt. Gox and Mizuho on Friday in the Ontario Superior Court of Justice. It accused Mizuho of knowing of Mt. Goxs fraud, of not segregating funds that belong to Mt. Gox from those of its customers and of continuing to provide banking services that inflated losses for bitcoin customers.