Hi @Anonymous,
As you said ,the offset 9:00 come from Japan STD time difference from GMT, if you have choose the Time zone when create the event in outlook, and don't want offset to be exist in google calendar, you could subtract the 9 hours befroe create the event in google calendar.

The expression in the "Start time" field of "Create an event" action of google calendar as below:
addHours(body('Create_event_(V2)')['Start'],-9)
The expression in the "End time" field of "Create an event" action of google calendar as below:
addHours(body('Create_event_(V2)')['End'],-9)
The flow would run successfully as below:

Please let me know if your problem could be solved.
Best regards,
Alice