Silent Sky is a combination of the additional episodes 13 and 14. It consists of the story in the future, three months after the incident that was similar to "New Generation Madness" and the disease Chaos Child Syndrome that brought by the past earthquake in Shibuya.

After surviving the onslaught at Sarugaku headquarters, Sousuke Banba resumes his investigation of the Kagewani monster hybrids. Armed with the ability to harness the Kagewani's power, the researcher now has a means to eliminate the creatures. But despite the benefits of this skill, it has one major drawback: Sousuke now struggles to maintain his sanity, with the power threatening to consume his body. Soon, threats old and new begin to rear their heads, as the upper echelons of Sarugaku become active once again and an assassin with a personal vendetta sets her sights on Sousuke. Nevertheless, he resolutely forges ahead on his mission, determined to track down the origins of the Kagewani and eliminate their threat once and for all. [Written by MAL Rewrite]

A floating space without gravity where an infinite number of lights shine in different colors: The "Box of Wisdom." Inside of this box, there are multiple worlds, multiple timelines, and there used to be many different people. This is where Dual and Dorothy were fighting with enemies called "Viruses." Worlds infected by viruses must be erased. That is the duty, the job of these girls. However, one day, Dual and Dorothy feel the presence of a new Virus. Arriving at the scene, they see a girl being attacked by Viruses. After saving the girl, the duo wait for her to awaken so they can ask who she is, where she came from, and where she is going. Finally, when the girl opened her eyes, she gave her name, Rimo, and whispered only one sentence... "I must return to the flower patch..." (Source: ANN)

At Maigahara Music College Affiliate School Maigahara Senior High (abbreviated as MaiMai) that gathers the most promising musical talents, there's a rumor circulating among students. "If you give an amazing performance at the school festival, you get special extra credit (or so they say)." Serina's grades are not very good, so she immediately believes the rumor and decides to form a band.