After graduating from Kyoto University of Education, he joined Mitsubishi Motors in 1967.
In October 1969, Onishi was selected Japan national team for 1970 World Cup qualification.
In 2002, he signed with Thespa Kusatsu and became a general manager.
On June 29, 2006, Onishi died of lung cancer in Yokohama at the age of 63.
This biographical article related to a Japanese association football defender born in the 1940s is a stub.