For travel from Japan to Kenya, PCR testing is not required for the trip to Kenya from March 11, 2022, as long as you have proof of vaccination (2 doses) and have registered on the vaccine and test registration website (Panabios.org) operated by the African CDC and obtained a QR code.
The return to Japan has also been eased as of June 1, 2022, so the vaccination certificate and PCR test upon return are no longer required for those returning from Kenya. According to the information on June 2, 2022, it took about 30 minutes to complete the procedure, which used to take about 4 hours.