Dr. Mukai was born in 1952 in Tatebayashi, Gunma. She received her Doctor of Medicine degree in 1977 and Doctorate in Physiology in 1988, from Keio University School of Medicine.
In 1989, she became a board-certified cardiovascular surgeon in the Japan Surgical Society.
From 1977 through 1978, Dr. Mukai worked as a resident in General Surgery, Keio University Hospital. She was on the medical staff in General Surgery, Shimizu General Hospital in Shizuoka in 1978 and on the medical staff in Emergency Surgery, Saiseikai Kanagawa Hospital in Kanagawa in 1979. Dr. Mukai began her work as a resident in Cardiovascular Surgery, Keio University Hospital in 1980, and served on the medical staff in Cardiovascular Surgery, Saiseikai Utsunomiya Hospital in Tochigi in 1982. She returned to Keio University Hospital in 1983 as the chief resident in Cardiovascular Surgery and was later promoted to an assistant professor of the Department of Cardiovascular Surgery, Keio University.
In 1985, Dr. Mukai was selected by the National Space Development Agency of Japan (NASDA, currently Japan Aerospace Exploration Agency) as one of the three Japanese Payload Specialists (PSs) for the First Material Processing Test (FMPT), which flew on the STS-47 (Spacelab) mission.
In July 1994, she flew as a PS on the STS-65 (the Second International Microgravity Laboratory: IML-2) mission, which consisted of 82 life science (human physiology, space biology, radiation biology and bioprocess) and microgravity science (material and fluid science, research on microgravity environment and countermeasures) experiments.
As a NASDA science astronaut, she became a visiting scientist of the Division of Cardiovascular Physiology, Space Biomedical Research Institute, NASA Johnson Space Center (JSC), from 1987 through 1988.
From 1992, Dr. Mukai worked as a research instructor in the Department of Surgery, Baylor College of Houston, as well as serving as a visiting professor of the Department of Surgery, Keio University school of Medicine from 1992 to 1998.
During the STS-47 (Spacelab J) mission in 1992 and the STS-90 (Neurolab) mission in 1998, Dr. Mukai served as a Spacelab communicator for crew science operations as a backup PS. In October 1998, she flew on the STS-95 mission as a PS along with US Senator John Glenn, the first American astronaut to orbit the Earth. During the STS-95 mission, she conducted various life science and space medicine experiments.
In August 2000, Dr. Mukai was assigned as a deputy mission scientist for the STS-107 mission to coordinate science operations for the mission, which was launched in January 2003.
From September 2004 through September 2007, she worked as a visiting professor at the International Space University (ISU). She provided her specialized knowledge on space medicine and human space exploration health management for the ISU Master Program students.
From October 2007 through March 2011, she served as Director of the Space Biomedical Research Office, Human Space Technology and Astronaut Department, Human Space System and Utilization Mission Directorate of the Japan Aerospace Exploration Agency (JAXA).
From April 2011, Dr. Mukai has been serving as Senior Advisor to the JAXA Executive Director.