Center fielder Toma Mizoguchi went 3-for-4 with a tiebreaking triple in a four-run second inning as Keio beat Matsusho Gakuen of Nagano Prefecture 6-4 in the National High School Championship on Tuesday.
Yuta Saito hit a game-tying RBI single and Kenshiro Naito also singled in a run in the key inning, helping the Kanagawa school earn its first win in the annual championship for the first time in 46 years.
In other action at Koshien Stadium, Toyama's Takaoka Shogyo downed Aichi's Obu 5-1 after Tatsuya Abe broke a 1-1 tie with a two-run RBI triple and Shingo Nomura and Naoya Kitada added RBI hits in a four-run seventh.
Aomori Yamada and tournament debutant Honjo Daiichi of Saitama also advanced to the second round.