Ifrit, who has been trapped in Rimuru due to the latter's Predator skill, recaps events of the season while in a discussion with Veldora as they play Shogi.

The film's story begins when Arata inadvertently touches "Hermes Apocrypha," Lilith's Grimoire. Suddenly, he is enveloped by a bright white light, and a girl appears before him. She calls herself Lilim, and treats both Arata and Lilith as her parents. At the same time she appears, something changes in the world. The forbidden Eternal Library awakens. In the Library is sealed the ultimate culmination of Alchemy, the White Demon Lord. The White Demon Lord plots to eliminate Arata and the Trinity Seven to usurp the position of Demon Lord. Bristling with untold power, the White Demon Lord attacks Arata, and triggers a desperate crisis where Arata and the Trinity Seven must save the world in this last battle. (Source: ANN)

Heavens Library to Crimson Lord brings back Arata, Lilith, and the rest of the Trinity Seven to face off against the greatest enemy in the history of the Trinity Seven; Lilith's own father, who is revealed to be the strongest Demon Lord, challenges Arata who is now a Demon Lord candidate. (Source: Avex Pictures, edited)

Eli, Chihiro, and Miyako try to form a band but end up looking to Katsuragi for help. In the process they meet Kanon and become friends/ rivals. (Source: ANN)