>>109466992No, they're suing him in the US because that's part of the DMCA process. Youtube's TOS requires claimants file their DMCA lawsuits in a US federal court with San Jose in its jurisdiction, regardless of where the claimant and respondent actually reside/do business.
The fact he’s unlikely to even show up (or send expensive representation on his behalf) which will result in a default judgement, and the fact that Cover can use the result to go after him in Japanese courts both to collect and to add “malicious interference with business” to the charges, is just a bonus for Cover.