Daisuke Nikaidou became Meisei Academy's ace pitcher, a position influenced by the coach's favoritism rather than pure merit. He possessed a fierce desire to pitch, complicated by a heart condition diagnosed in his first year of junior high, which he concealed from his teammates; only his family, doctor, and team manager Kuroyanagi knew. Soichiro Tachibana primarily caught for him as pitcher, succeeding Tadashi Imagawa in that role. Tadashi later offered to catch "for old times' sake" during a practice session without Soichiro.

Nikaidou underwent necessary surgery without expecting to survive, though his father believed in his recovery. The surgery succeeded, granting Nikaidou what he called a "new lease on life." Following recovery, he chose not to return to baseball during high school. He expressed no regret over his time as pitcher, which had prevented Toma Tachibana from taking the mound. After the full revelation of Nikaidou's health and departure, no resentment lingered between the Tachibana family and Nikaidou. Without apologies, they reached a mutual understanding.

Nikaidou remained a steadfast supporter of the Meisei baseball team, regularly attending games while managing his health. During a specific match against Seinan, his difficult inning contributed to Meisei's loss. This event later prompted Seinan's pitcher to approach the Tachibana brothers about transferring schools.