Rentaro had set up an outdoor classroom for the kids in the outer district and was enjoying class. Seitenshi suddenly appears and lets him know that one of the Monoliths is about to be destroyed.

Rentaro is condemned for a decision he made in battle, and is told that there is another Gastrea named Pleiades that is protecting the already supposedly immortal Aldebaran. Rentaro is forced to face the enemy alone, and is helped by someone rather unexpected: his enemy from the past.