Introduction
Corundum is cheerful and always enjoys getting together with friends.
Corundum is the childhood friend of Pyrope, who is too shy to speak, and Corundum is the only one Pyrope talks to. Attacking by the stones on his neck is his expression of affection, sometimes making troubles.
Corundum enjoys all games about balloons. He is not afraid of popping, and he is a little interested in poppong a normal balloon by getting on it.