Marubeni is leading the 12-member consortium behind the floating wind project, which lies 20 kilometres off the coast of Fukushima.
A five-year trial will see different floating structures being tested including three wind turbines and one sub-station.
The ¥18.8 billion ($189 million) Fukushima Mirai project has been sponsored by the Ministry of Economy, Trade and Industry and the first turbine is expected to come online in November.
John Deasey, Trelleborg’s renewables sales manager, said: "The initial supply from Trelleborg is for cable buoyancy and protection for the first wind turbine, with the remainder of the project to be completed between 2013 and 2015.
"Securing this contract is a significant achievement for Trelleborg and follows on from previous contract wins in this growing sector, such as the Statoil Hywind project off the coast of Norway and the Windfloat project off the coast of Portugal."
Trelleborg’s buoyancy modules are designed to protect power cables from excessive movement and bending that could cause them damage.