Osaka is 7 hours ahead of Copenhagen
Best overlap: 8:00 AM to 11:00 AM in Copenhagen is 3:00 PM to 6:00 PM in Osaka.
For a call that suits both sides, look at 8:00 AM to 11:00 AM in Copenhagen / 3:00 PM to 6:00 PM in Osaka. Around 3 hours of overlap is enough to work comfortably, as long as meetings don't drift to the end of one team's day. Finally, Copenhagen observes daylight saving and Osaka doesn't, so this window shifts by an hour for part of the year — recheck it each spring and autumn.