SB & Mitsui will continue to work on renewable-energy projects together, according to an online statement.
They did not reveal the PV module supplier for the array, which spans across 53.1 hectares of land in Hamamatsu, Shizuoka prefecture.
It is expected to annually generate enough electricity to cater to the needs of roughly 15,000 homes.
SB Energy — which also develops wind projects — had completed 260.2 MW of solar capacity by the end of June, with an additional 304 MW under construction throughout Japan.
Earlier this month, it scrapped plans to build its first offshore wind project — a 100 MW array off the coast of Kashima, Ibaraki prefecture — following disagreements with its partners over the feasibility of the site.