Teitoku Kakine

Dark Matter, Rhinoceros Beetle 05, 垣根帝督

One of the seven Level 5 espers is this person, ranking second after Accelerator in power. They lead SCHOOL, an underground faction. Their ability is producing Dark Matter, a substance that shouldn't exist in this world, making them the opposite of Accelerator who specializes in destruction. This individual competes with Mugino Shizuri, leader of ITEM and number #4 Level 5 esper Meltdowner. They aim to become the strongest, even if it means killing off Accelerator. Despite being ruthless, cocky, and coldhearted, they show no mercy or compassion towards their enemies or bystanders and look down on anyone they deem inferior.

Spoilers:

In the war between the underground factions of Academy City, Kakine fights Accelerator but loses. Yomikawa stopped Accelerator from killing Kakine but Kakine stabs her from behind, causing Accelerator to go berserk and kill Kakine in a gruesome way- going as far as tearing him into countless pieces.But later Kakine reappears in New Testament and features prominently in the sixth volume. It was revealed that he wasn't actually dead but his body was preserved by the Kiharas. He learns to copy human cells thanks to Kihara Byouri using his power in Baggage City, resulting in him becoming able to create even his own body. In the war between the underground factions of Academy City, Kakine fights Accelerator but loses. Yomikawa stopped Accelerator from killing Kakine but Kakine stabs her from behind, causing Accelerator to go berserk and kill Kakine in a gruesome way- going as far as tearing him into countless pieces.But later Kakine reappears in New Testament and features prominently in the sixth volume. It was revealed that he wasnt actually dead but his body was preserved by the Kiharas.