On the 5th, Seibu Lions announced that they had reached an agreement to sign infielder Kazunari Ishii who had declared free agency from Nippon-Ham.

Hiroike, the team's general manager, stated through the baseball team, "We are very happy to have acquired Ishii, who we expect will make a significant contribution to The Lions in both offensive and defensive areas. After setting career highs in a number of hitting metrics this season, as well as making excellent contributions to the second baseman defense team, Ishii has shown great potential to continue to improve his performance in the future. I hope that the addition of Ishii will bring more competition to the The Lions infield lineup, and I hope that this competition will strengthen our team.

Ishii joined Nippon-Ham as the second pick in the 2016 draft and played in 114 games from his first year in 2017. From 2021, he played in 100 games for two consecutive years, and this season he played in 108 games, batting .259 with 6 Home Run and 30 RBI.