The 11-member group has completed the installation of the high-voltage undersea cable and a dynamic cable, which follows the floating equipments' movements as well as wave and tide actions.
The cables connect the onshore substation, a 2MW floating wind turbine and a 66kV floating substation.
Shipbuilder Japan Marine United and the University of Tokyo developed the floating substation. The turbine, which rests on a semi-submersible foundation, was built by Mitsui.
The ¥18.8 billion ($189 million) Fukushima Mirai project has been sponsored by the Ministry of Economy, Trade and Industry since March 2012.
Phase two, which is scheduled for commissioning in 2015, will see a 7MW Mitsubishi hydraulic turbine mounted on a three-column semi-submersible platform, also built by Mitsubishi.