The Hombo family, owners of Mars Whisky, first took out a license to distil whisky in 1949, although it was not until 1960 that it started making whisky ? and not in Kagoshima, but at a purpose built plant in Yamanashi. Iwai was also responsible for the design of their pot stills and is considered a pioneer in the history and development of pot still whisky in Japan.

Aged in Sherry, Bourbon and American white oak casks. 'COSMO' is the name of a mountain in the Japan Central Alps close to the Mars distillery.