Trust, innovation, communication, and leadership are all values that have been at the heart of Mitsui's business management philosophy since the early 18th century, so it should come as no surprise that Mitsui seeks to build its partnership upon a foundation of such values. 

In 2010, when Mitsui saw the opportunity to invest in the onshore boom in shale gas production occurring in the U.S., it knew that it would need to forge partnership with only the most skilled and industry-savvy players in the field. At that time, besides being highly seasoned and financially strong oil & gas operating companies, both Anadarko E&P Onshore LLC and Chesapeake Appalachia LLC controlled multiple large swaths of leases throughout central and northeastern Pennsylvania, all of which targeted development of the Marcellus Shale formation. After successful negotiations, Mitsui was able to contractually gain entrance into several joint development agreements Anadarko and Chesapeake already had in place. Mitsui was then a full-fledged interest owner in Marcellus leases. Mitsui E&P USA LLC was established at the acquisition of the Marcellus shale asset, to develop a new phase of Mitsui's E&P business portfolio in North America. 

Subsequently, through its new connections and partners, Mitsui had the opportunity to enter into another shale venture, this time in South Texas, targeting the Eagle Ford formation. In 2011, it closed on its joint development agreement with Colorado-based SM Energy Company. The asset operator, Anadarko, sold its working interest to Mesquite Energy Inc. (formerly Sanchez Energy) and Blackstone in 2017. SM Energy Company sold its working interest to KKR/Venado. 

On the part of Marcellus, Anadarko divestest all of its Marcellus assets. Mitsui also divested its assets in the Anadarko-operated acreage to the same buyer, Alta Resources. The transactions of Mitsui were completed in June 2017. 

Mitsui's solid and healthy relationship with these partners and new partners has paved the way for its continued success in these assets, and has made possible its presence and participation in America's historic shale gas revolution.​