|Air Date||November 4, 2011|
|Opening Song||My Dearest|
Solution:Flux is the fourth episode of the Guilty Crown anime. It first aired on November 4, 2011.
Shu is arrested by the GHQ, much to his classmates' shock and worry. He is sent to GHQ Isolation Facility Four where he remains silent about Funeral Parlor. Upon learning that Gai and his crew plan to attack the Facility to rescue their "comrade," Major Seiga brings Shu to the Isolation ward, revealing that Yahiro sold him out so his brother, a victim of the Apocalypse Virus, would receive treatment. Furthermore, Major Seiga justifies GHQ's harsher actions as being for the safety of Japan, using Shu's feelings for Inori and his doubts about Gai against him.
He reveals that the "comrade" Gai wants to rescue is mass murderer Kenji Kido, which makes Shu further question Gai's trustworthiness. The Major gives Shu a transmitter disguised as a pen that he is to use if he comes into contact with Gai. Later that night, a disguised Gai visits Shu and tells him his plans to rescue Kenji; Shu claims that he doesn't want to be involved. Tsugumi informs the two that Inori has disobeyed Gai's orders to stand by in order to rescue Shu. Shu, worried, goes to save her, forcing Gai to change his plan.
Protected by Ayase's Endlave Steiner, Shu heads towards where Inori is and encounters Kenji himself along the way. He uses Kenji's Void, a Gravity gun, to stop the GHQ Endlaves and rescue Inori. After Isolation Facility's destruction, Gai proposes that Shu follow him. Shu reluctantly agrees, although he keeps the transmitter given to him and does not inform Gai of his exchange with the Major.