Toyama University Hospital said three surgical teams on Friday successfully extracted the heart, liver and kidneys from a boy who was declared brain-dead.
The boy's heart was successfully transplanted into a girl under the age of 10 in Osaka Prefecture later in the day.
The liver will go to another girl in Tokyo, also younger than 10, and the kidneys will be transplanted to a woman in her 60s in the city of Toyama, the Japan Organ Transplant Network said.