Dr. Okamoto started his career with Tokyo Electric Power Company (TEPCO) in 1993.

In TEPCO, he has worked for the number of projects related to electric power systems including,
- Research on dynamic security assessment and optimal power flow on deregulated electric power systems
- Project management of Ultra High Voltage (UHV) AC transmission (1000 kV)
- Renewable energy integration to the power grid and frequency control of inter-area power systems
- Smart grid strategy
- Project management of international consultancy services for the several electric power companies
- Regulatory affairs of Japanese electricity market reform.

Since June 2021, he has been EVP of TEPCO Power Grid. Prior to the current position, he served as Executive Managing Officer of TEPCO Holdings, President of TEPCO Research Institute.

In 2017, Dr. Okamoto jointly published a book entitled “Utility 3.0: Game change in energy industry 2050”. He also published many articles and several books regarding electric power systems.

Currently, he is member of Market Strategy Board of International Electro-technical Commission (IEC/MSB), member of Steering Committee of CIGRE, and chairman of the National Committee of CIGRE of Japan.