Kadokawa Corp. said Friday it confirmed that the personal information of all employees of its subsidiary operating the popular video streaming website niconico was leaked in a recent massive cyberattack affecting the group’s websites. The findings were announced a day after a group purporting to be a Russia-linked BlackSuit ransomware gang claimed responsibility for a cyberattack against Kadokawa’s networks, insisting that it has stolen employee-related data and internal-use documents, among other information. The Japanese publisher said it is still investigating the veracity of the group’s cl…