Intrigued by Phos's new fighting ability, Bort asks them to become their partner in place of Diamond while Kongō is asleep. The next day, another new type of giant Lunarian appears, proving resilient to Bort and Phos's attacks. As Phos and Bort retreat and order the other Lustrous to hold their position, the Lunarian makes its way inside the school and starts chasing after Diamond. Feeling that they cannot rely on Bort to protect them, Diamond goes up against the Lunarian, using their diamond limbs to slice it...