Eiensei Riron

Eiensei Riron (永遠性理論, Eiensei Riron) is sung by. The song lyrics were written by, and the song was composed by.

Eiensei Riron was originally released within the game on February 20, 2019. It becomes available in normal lives after clearing Part 4 Chapter 1.2. Eiensei Riron was released on January 22, 2020 as part of the Re-raise Single, which can be purchased digitally on the iTunes Store, animelo mix, music.jp, mora, and Recochoku (レコチョク).