Police in Tokyo have launched the investigation after the body of Rika Okada was found in a storage lock-up, England’s Mirror has reported.
The 29-year-old nurse, missing since late March, was found in a two-metre box with multiple stab wounds.
Ms Okada’s credit card had been used to pay for the short-term rental of the lock-up, as well as the delivery of the package from the southern city of Osaka to Tokyo.
Local media reports state that a woman used Ms Okada's passport to leave the country earlier this month.
The schoolmate, who was not named, is believed to have lived just a few hundred yards from the lock-up with a Chinese woman of about the same age.
Both women flew from Tokyo's Haneda airport on the same flight, bound for Shanghai.
Just before she went missing, Okada wrote on her Facebook page that she was going to meet up with an old friend whom she had not seen for a decade.
