When he discovered that going to an acting school wasn't the same as meeting the people he admired on TV, he wanted to quit, but by that time he had been selected to play a small role in a 'Vampire', a television movie being filmed by Fuji Television.

This role launched his reluctant career, and though he purposely took a number of years off work to try studying, his failing to get into university urged him to continue in the acting business.

Mizutani stars in a regular TV Asahi detective drama called Aibō (相棒) with actors Yasufumi Terawaki (2000-2008, 2022-), Mitsuhiro Oikawa (2009-2012), Hiroki Narimiya (2012-2015) and Takashi Sorimachi (2015-2022).

In addition to acting, his agency, "TRI-SUM", also encouraged him to put out music albums starting from 1977, all of which sold very well.

He is now married to singer and actress Ran Itō from the 1970s Japanese idol trio Candies; they have one daughter.