After overcoming various tumultuous events, mercenary sergeant Sousuke Sagara of Mithril and "Whispered" school girl Kaname Chidori return to their normal high school lives. Sousuke continues his efforts to assimilate with the civilian population and manage his mission at the same time, while Kaname attempts to support his endeavors (even though his antics often drive her up a wall). However, as their lives calm, new problems begin to appear. The appearance of an independent terrorist organization known as Amalgam and internal conflicts within Mithril threaten to wreak unity into a series of failures and betrayals. And new, powerful Arm Slave models only worsen the situation when the world's peace is at stake. As Kaname and Sousuke face their own inner battles amidst life-threatening fights, will they be able to make the right choices and change their future? [Written by MAL Rewrite]

With the tumultuous cultural festival behind him, Masamune Makabe continues his efforts to carry out his revenge: to make the "Cruel Princess" Aki Adagaki deeply fall for him and then immediately dump her. As his class is going on a trip to Paris, widely known as the City of Love, Masamune has the perfect opportunity to get even for his childhood heartbreak. Before Masamune can impress Aki, the two meet Muriel Besson, a French high school otaku who aspires to create a romantic comedy manga series. Muriel believes Masamune is the ideal model for the protagonist and asks for his help. The boy reluctantly agrees, dragging Aki along to provide inspiration for the love interest's character. But to do so, the two must show Muriel what Japanese love is like. To make matters more complicated, Kanetsugu Gasou is masquerading as Aki's childhood friend, Masamune, to trick and use her. With mix-ups and love rivals galore, Masamune's revenge is proving to be quite the difficult task.

While searching through his grandfather's attic, Hikaru Shindou stumbles upon an old go board. Touching it, he is greeted by a mysterious voice, and soon after falls unconscious. When he regains his senses, he discovers that the voice is still present and belongs to Sai Fujiwara no, the spirit of an ancient go expert. A go instructor for the Japanese Emperor in the Heian Era, Sai's passion for the game transcends time and space, allowing him to continue playing his beloved game as a ghostly entity. Sai's ultimate goal is to master a divine go technique that no player has achieved so far, and he seeks to accomplish this by playing the board game through Hikaru. Despite having no interest in board games, Hikaru reluctantly agrees to play, executing moves as instructed by Sai. However, when he encounters the young go prodigy Akira Touya, a passion for the game is slowly ignited within him. Inspired by his newfound rival, Hikaru's journey into the world of go is just beginning. [Written by MAL Rewrite]

The fourth season of FLCL, and sequel to FLCL Alternative. It centers on three teenagers who graduated and have started working. The CGI anime will have a theme of the feeling of being an adult.