Monex Group was sued in Japan over the sale of Credit Suisse’s riskiest debt, making the online brokerage a rare case of a financial institution being accused of responsibility for investor losses triggered by Switzerland’s move to wipe out the bonds.

Kojimachi Oodori Sogo Law Office filed a suit Thursday against the firm with the Tokyo District Court on behalf of an individual investor seeking about ¥22.5 million ($161,000) in compensation.

The 62-year-old plaintiff is accusing Monex of having sold him the securities via its business partner Wealth Guardian, without providing any explanation on so-called special viability risks related to the debt, according to a copy of the complaint seen by Bloomberg News.