Critical & Demon Lord is the twenty-third chapter of the Trinity Seven manga series, released on October 9, 2012 in Monthly Dragon Age November 2012, and later compiled in the fifth volume on January 7, 2013.
As Arata and Mira are surrounded by the Ilias Fragment's spectres, "Hijiri" declares that Arata should remain together with her in the barrier until the real Hijiri has finished destroying the world. The two discuss that their situation has become worse since not only are they unable to use thier magic while surrounded by strong enemies, but Sora has also been sealed. Although, "Hijiri" corrects them, stating that Arata was important to both the grimoire and her master; only Mira is currently in danger. Arata then adressess the Ilias Fragment, who insists that he call her using Hijiri's nickname, Ilia, that Mira, despite her appearance, is his boss. Nevertheless, Ilia proposes to Arata that if he stays with her, she will give him a wonderful life before displaying to Arata of a a vision of Hijiri in a naked apron tending to his needs. After Arata returns to his senses, Mira can already guess the type of vision he saw upon seeing the look on his face. Ilia further offers that if Hijiri was not enough, she can transform to her original form, which is more mature than Sora's, much to Arata's curiosity and Mira's chagrin. Suddenly, Arata is able to hear Sora's voice in his head who discreetly explains to him the box entrapping her is also the linchpin to the barrier. In order to escape from the barrier, Sora requests that Arata distract Ilia while she makes several attempts to destroy the linchpin. Following through with their plan, Arata tells Ilia that he will comply with her demands, but also asks that she release Mira despite the Trinity Seven's objections. Even though Ilia agrees with his condition, Mira implores Arata need not sacrifice himself for her since he is only a temporary member of Grimoire Security. Nonetheless, Arata aplogizes to her, hoping that she will save them after leaving the barrier. As Ilia approaches Arata, he asks her if Sora will die while imprisoned in the seal. Ilia explains that grimoires cannot die and that being forgotten for eternity is their death. Arata then comments that their fate is quite lonely to which the grimoire remarks that he is kind for caring in spite of them being tools. Lastly, Arata questions if Hijiri did indeed say that she will annihilate the world. The Ilias Fragment confirms this, but also states that the Hijiri in his memories no longer existed. Moreover, she tearfully suggests to a confused Arata that once the world has been erased, he should go talk with the real Hijri after everything is over. Returning her attention to Mira, Ilia then orders her spectres to continue attacking. Explaining to a shocked Arata that that since there is no alternative to leave the barrier safely, she will simply have to kill Mira. Wehn Arata attempts to help Mira, he finds himself restrained by Ilia. The grimoire reveals that she had predicted that he and Sora would communicate telepathically, so she decided to restrict him to prevent him from interfering. Ilia further explains to him that a girl in love will become possessive of the person of her affection. Next, Sora suddenly begins to feel her magic being absorbed within the seal, realizing that Ilia planned to use her for as a power source henceforth. Mira calls Ilia a coward, but the grimoire simply retorts that in the goal of magic is to achive through any means necessary. Although Mira reluctantly agrees with her statement, she is pinned to the ground by the spectres before she can argue further, as Ilia no longer cares because Mira will die regardless. Meanwhile, Arata continues to be restrained; the boy implores Ilia to cease her actions since he is the her true target. Unfortunately, Ilia ignores his pleas, advising that he not worry for other girls or Hijiri would become envious. Instead, she insists that he sit and witness the type of punishiment Hijiri would inflict on girls who become close to him, as well as the transformation of his grimoire into a spectre. As Mira and Sora scream in pain, Arata suddenly yells Ilia's name, surprising her as his eyes grow dark. While Ilia is startled by his sudden change in demeanor, Arata divulges to her that he is most happy when his friends laughing and enjoying themselves together, much to Ilia's confusion. Arata then recalls that he was unable to save Hijiri, and presently both Mira and Sora will also both disappear as well. Furstrated at failing to protect those he cares about again and being unable to control his magic, the Demon Lord Candidate expresses that he has not truly been ruling as his magic unexpectedly begins to rise. Sora then orders Ilia to stop her master, but before Ilia can act, a dark aura abruptly engulfs Arata and transforms his appearance. While Mira and Sora stare in shock, Ilia is greatly frightened by the figure in front of her. Sora explains that the being before them is the Demon Lord manisfestation within Arata, Astral Trinity. As Astral Trinity is fully revealed, Ilia can only meekly call out Arata's name.
In the beginning of the chaper, Ilia suggests to Arata that he should remain with her in the barrier Hijiri has finished destorying the world. This is a continuation of the last scene from the previous chapter where she she tells him the same recommendation.
Arata and Mira recap that no only are they unable to use their magic, but Sora has also been captured as well.
The two discovered that their magic was sealed in Ilias & Adventure when Mira attempted to remove a group of spectres, but instead resulted in her clothes being torn away.
Sora's capture occurred in the previous chapter during her battle against Ilia when the latter calculatingly trapped Sora after catching her off guard.
In an attempt to stall Ilia, Arata decides to accept her demands in exchange for Mira's departure from the barrier. Despite the Trinity Seven's objection, Arata explains that as the second seat of Grimoire Security, his duty is prioritize the safety of his leader. In Second Security & Dimension Trouble, Arata was temporarily inducted into the organization by Master Biblia to accompany Mira and Akio's investigation to the Libel Academy's destruction.
Upon Ilia's endeavor to eliminate to Mira and drain Sora, Arata recalls being unable to prevent Hijiri from disappearing. This is a reference to the events before Cracker & Third Selection where a Breakdown Phenomenon occured in Arata's hometown, causing Hijiri to hand Sora to Arata at the cost of herself disappearing.