Shimada-sensei was Matsutaro Sakaguchi's homeroom teacher in middle school. After Matsutaro's expulsion for stealing a truck and endangering the public, Shimada-sensei actively helped him find employment. He arranged job interviews and personally accompanied Matsutaro to potential workplaces, showing commitment to his student's future despite Matsutaro's delinquent history and lack of cooperation during the search.

Shimada-sensei tried to mediate when Matsutaro provoked professional sumo wrestlers at a restaurant. Matsutaro refused to apologize, escalating the confrontation until he was physically subdued.

Later, Shimada-sensei attended Matsutaro's crucial sumo match against Kondo, where the winner would earn promotion to the professional Juryo division. He watched from the audience alongside Matsutaro's family and former teacher, Reiko Minami.