Kusha school 

One of the so-called ‘Six Schools of Nara Buddhism’ that appeared in Japan during the early period of Buddhism's development. More an area of specialized study than a school as such, this group of scholarly monks concentrated on the study and teaching of the Indian Buddhist master Vasubandhu's Abhidharma-kośa, a compendium of Sarvāstivādin teachings. These scholars saw themselves as successors to the Kośa school in China.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)