He is a member of the theatrical and musical unit TEAM NACS, and is represented by Creative Office Cue.

In 1995, while still in university, Oizumi debuted as an entertainer on the late-night program Mosaic nights aired in Hokkaidō.

[3] After failing his entrance exams two years in a row, in 1994, he entered the Hokkai Gakuen University to study business.

[4] In 1996, he organized the theatrical company TEAM NACS with his friends, Hiroyuki Morisaki, Ken Yasuda, Shigeyuki Totsugi, Takuma Oto'o.

[9] In October 1995, when Oizumi was still in university, he debuted as an entertainer through his portrayal of 2nd generation Genki-kun on the late-night program Mosaic nights aired on HTB.

He was chosen after the program staff were searching for Mamoru Tanaka, the original Genki-kun, and Oizumi was introduced to the director by Ito Ayumi, the wife of Takayuki Suzui.