Kanzei first baseman Takaki Morimoto singled home the go-ahead run in the fourth inning Monday as the Okayama school defeated Kyushu Gakuin 5-2 in the 74th national high school baseball invitational tournament.
An RBI single by infielder Yoshitaka Mizumata tied the score 1-1 in the third before Morimoto's tie-breaking hit gave support to southpaw Ken Miyamoto, who held Kyushu Gakuin to one run the rest of the way while giving up seven hits without a walk over the distance.
Jinsei Gakuin and Fukui Shogyo joined Kanzei in the quarterfinals with second-round victories at Koshien Stadium.
In the day's second game, Jinsei broke a scoreless deadlock with four runs on four consecutive hits in the ninth inning and starter Atsushi Inoue held on to survive a shaky bottom half as the Kagawa school edged Toyama's Shinminato 4-2.
In the third game, first baseman Yoshinao Akado hit a grand slam in the first inning to pace Fukui Shogyo's 12-hit attack and Keisuke Nakaya pitched a four-hit complete game in an 8-2 rout of Tsuda Gakuen of Mie Prefecture.
Fukui Shogyo advanced to the quarterfinals for the first time in 24 years.