Clarke finished the first round on 66, six under par, after chipping in for an eagle at the par-five 3rd, and he carded four more birdies at the 7,072-yard Taiheiyo Club Gotemba course.
The Briton shared the lead with Naomichi Ozaki, Hajime Meshiai, Hirofumi Miyase and Hideki Kase.
Clarke's Ryder Cup team-mate, Lee Westwood, who won this event last year, made a steady start to his defence, ending the first round handily poised one stroke behind the pacesetters.
Ozaki made an encouraging start in his quest for a fourth victory of the season on the Japanese tour, with one bogey and seven birdies.
The winner of the tournament stands to collect around pounds 170,000 in prize money.
TAIHEIYO MASTERS (Gotemba, Japan) Leading first-round scores (Japan unless stated): 66 N Ozaki, H Meshiai, H Miyase, H Kase, D Clarke (GB); 67 R Kawagishi, T Ozaki, T Suzuki, L Westwood (GB); 68 T Izawa, K Yokoo, K Kuwabara, S Maruyama, K Takami, H Fujita, F Minoza (Phil).Reuse content