Adamant Sensei

Японское имя:	金剛先生
Прозвище:	Sensei

Adamant-sensei (金剛先生/Kongō-sensei; lit. Adamant Teacher) is the head of the Gems, the teacher, protector, and father figure. He teaches the Gems about the current world and its history, and decides a role suited for each of them. He has overwhelming offensive power and can disperse the Moon People in one blow. Very scary when angered.

Every time the Moon People come, one Gem from a pair of patrol will ring the bell. He and some (or all) Gems will go to the scene and disperse the Moon People. Unlike the younger Gems, he can stay awake for a long time and doesn't require sleep, though he can be sleepy and still sleeps during "meditation". When angry, he could crack the entire building and his voice is able to shatter the weaker Gems in close range. Later it shown that he dispersed the Moon People by cracking his arm and used very tiny fragments of himself to attack them.

According to Jade, waking up sensei from his "nap" is more of a struggle than fighting the Moon People.

The Gems love being patted by him.