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?

The band given—comprised of Ritsuka Uenoyama, Mafuyu Satou, Haruki Nakayama, and Akihiko Kaji—has advanced to the final screening of the Countdown-fes Amateur Contest, in which they will be judged on their live act. Although enthusiastic, they worry about having only one original song to perform. Mafuyu embraces the idea of learning more about music in order to create new, emotionally resonant songs. In this regard, he unexpectedly receives help from Ugetsu Murata, Akihiko's on-again, off-again lover. Ugetsu has unsuccessfully tried to let go of Akihiko, who himself is torn between lingering feelings for his past and an uncertain resolve for the future. As the competition draws near, Haruki uncharacteristically begins to doubt his place in the band and the trust he shares with Akihiko. It is a given that not all attachments last forever, but it remains to be seen what can be salvaged from the ruins of heartbreak—or if only regrets will endure.

The Band of the Hawk has dwindled in the year since Guts left them on his journey to forge his own destiny. Unaware of their fate, Guts returns to the Hawks—now being led by his former ally Casca—after a rumor about them passes his way. Once the saviors of the kingdom of Midland, the Band of the Hawk are now hunted as they desperately fight for their lives while plotting to free their leader, Griffith, after he was imprisoned for committing treason. But the man they save is far from the Griffith they remember. Griffith is a shell of his former charismatic self after a year of continuous, horrific torture. No longer able to walk, speak, or even hold a sword, he has nothing but the small, strange trinket, the Crimson Behelit, that will not leave him. The entire Band of the Hawk want to rise to greatness once more, but how much are they willing to sacrifice to return to their past glory? It doesn't seem possible, but when Griffith's heart darkens and a solar eclipse blackens the sky, the Behelit offers a choice that will leave the Band of the Hawk with a blood-soaked fate that will haunt them for the rest of their days.

Upon hearing news that islands in East Blue are being destroyed, Monkey D. Luffy and his crew go to investigate. On their way, however, an outlandish pirate ship appears out of the sky, helmed by the infamous pirate Shiki the Golden Lion—a man who ate the Float-Float Fruit and the first ever prisoner to escape from Impel Down. In his quest to defeat the World Government, Shiki kidnaps Nami to be his own navigator and sends the rest of the Straw Hat Pirates to his floating islands as hostages, leaving her in a dilemma. Separated in a land under Shiki's absolute control, Luffy and his crew must survive the mystifying terrain in order to bring back their navigator and friend.