He is a record producer from Michigan.
Combined, the blu-ray and DVD ranked #2 with over 32.000 units sold in Japan. See how it ranks with previous BABYMETAL releases.
Joakim Brodén, lead singer of Sabaton, and featured artist on "Oh! MAJINAI" from METAL GALAXY, talks a bit about the process of recording for it.
It appears to have been a very off-hand experience. He explained the process in a talk with Herman Li of Dragonforce.