After the Reflection, some of the people in all parts of the world are discovered with super powers. Some become heroes, and others villains. How did the Reflection happen? What was the cause of it? With many unsolved mysteries, the world is led into turmoil.

After destroying Earth many years ago, the alien race Gauna has been pursuing the remnants of humanity—which, having narrowly escaped, fled across the galaxy in a number of giant seed ships. In the year 3394, Nagate Tanikaze surfaces from his lifelong seclusion deep beneath the seed ship Sidonia in search of food on the upper levels, only to find himself dragged into events unfolding without his knowledge. When the Gauna begin their assault on Sidonia, it's up to Tanikaze—with the help of his fellow soldiers and friends Shizuka Hoshijiro, Izana Shinatose, and Yuhata Midorikawa—to defend humanity's last hope for survival, and defeat their alien foes. Sidonia no Kishi follows Tanikaze as he discovers the world that has been above him his entire life, and becomes the hero Sidonia needs. [Written by MAL Rewrite]

In Ikebukuro, the lives of its citizens continue intertwining with each other as if their fates are predestined. Mikado Ryuugamine is now one step closer to his goal of living an exciting life, and in turn, delves deeper into the darker side of Ikebukuro. After gaining absolute control over a former rival, he uses his newfound power as he pleases, purging the Dollars from the inside to mold it into the ideal organization. This proves to be as challenging as it sounds as Mikado must now deal with unwanted outside interference, most notably a re-emerging and dearly missed friend. Meanwhile, Izaya Orihara still has some schemes up his sleeve, although a rival information exchange center has proven to be quite the hindrance, lurking within everyone’s favorite downtown district. Undoubtedly, sooner or later, chaos will strike again. [Written by MAL Rewrite]

The story on Arcadia's mystery, on which the 13th television episode was based.