Kōki started playing little league baseball for the Tamashima Minami Elementary School and his team won runner up in the Okayama Prefectural Tournament during his 5th grade.[1] He initially started as an outfielder, but switched to a pitching role when he played for Kurosaki Junior High.[2] He went on to become the ace pitcher of Kurashiki Technical High, but his team never made it to either Spring Koshien or Summer Koshien.[3]
When he went undrafted after graduation, he joined the Industrial Leagues under Honda Suzuka. He spent his first 2 years mostly in the dug out due to injuries, but in the succeeding year, he came to the rescue as a reliever in a crucial match against JR Tokai and helped his team reach the final round of the 2014 Intercity Baseball Tournament.[4]
Hanshin Tigers
He was chosen as the Hanshin Tigers' 4th round pick in the 2014 Nippon Professional Baseball draft. He signed a 50 million yen contract with the Tigers, with an estimated 8.4 million yen annual salary. He was assigned the jersey number 43.[5][6]