October 4, 2017 vs Chunichi at Yokohama Stadium – Hamaguchi notched his tenth victory of the year and became the sixth Yokohama rookie pitcher to reach double-digits in wins, first since Takeo Kawamura in 1997; and the first Yokohama left-handed rookie to reach double-digits in wins since Takashi Suzuki in 1958.
October 19, 2017 vs Hiroshima at Mazda Stadium – Hamaguchi recorded the win and became the ninth rookie (accomplished eleven times) in Playoff/Climax Series history to notch a win. He is the first rookie in Yokohama Bay Stars history to record a post-season victory.
Hamaguchi recorded two wild pitches in the game (first and second inning) and became the fifth player (accomplished five times) to throw two wild pitches in one Player/Climax Series game. He joined Kenichi Nakata (2007, Final Stage, Game 3) as the only players to record two wild pitches in one game and get the win.
Source: Sponichi 10/20/2017