Shusaku Koishikawa (小石川 秀作 Koishikawa Shusaku) is a member of the Big K Karuta Society. He is a player with a track record of the All Japan Championship runner-up. This has mostly been due to many Otetsuki. He has worked at the Oishi Tengu Corporation which is a producer of karuta cards.
He makes plenty of blunders committing faults and double faults several times in a tournament. But he is such a good player that he can still be a runner-up despite his errors.
His current job at a karuta card factory has given him a deeper insight on the cards themselves, which he uses to his advantage in a match.