Rika Okada had been missing since late March.
According to the company that delivered the package, the order was paid in Okada's name. The 29-year-old's credit card was also used to rent the storage locker where her body was found.
Okada's body was found with more than a dozen stab wounds, but authorities say there were no defensive wounds to indicate a struggle.
Prior to disappearing, Okada posted on Facebook that she was going to visit an old friend.
Police have refused to confirm a report that a woman used Okada's passport earlier this month to leave the country and fly to Shanghai.