Complex sentence: Mifune eventually beats Tomonoura in a tight game and Goro and Toshiya vow to play on the same high school team together to defeat Kaido however when Mifune East's played Kaido Affiliate, they lost 19-0 in the 4th inning and the game was defaulted.
Split into simpler sentences: Mifune eventually beats Tomonoura in a tight game and Goro and Toshiya vow to play on the same high school team together to defeat Kaido. However, when Mifune East played Kaido Affiliate, they lost 19-0 in the 4th inning and the game was defaulted.