Yuito and Nagi's first mission as a part of the Seto Platoon takes them to Suzaku; when things get difficult, Kasane and Naomi from Kyoka Platoon come to their aid.

Yuito has several questions on his mind about a childhood incident; the Seto and Kyoka Platoons go on their next mission; Naomi puts herself in danger.

Naomi ends up becoming a serious threat to the Scarlet Guardians; Fubuki wants to keep everything under wraps; an injured Nagi recuperates at the hospital.

Even after being told the truth about Naomi, Nagi does not back down; a mysterious force sends Yuito and Kasane to a place where red strings are all they can see.

Discontented with the government, Karen supports Seiran's coup; circumstances indicate that Kasane murdered Yuito's father.

Kasane wake to a shocking reality and strange encounters; Kasane learns about the void in the sky and a way to stop it; Yuito and Kasane clash after she finds out what is behind Karen's revolt; Kasane heads to Seiran with other OSF members.