Tamoya Karasuma is the older brother of Tadaomi Karasuma, he's also a assassin named the 'Black Diamond'. Now that he is retired from assassinating targets, he is offered a job to be the new music and science teacher of class 3-E. But, he is no normal human teacher. He can go up to a speed of Mach 60, his hair and eyes can change colors from his mood, he can disappear and reappear anywhere in the world and universe, he can shape shift to look like any person of his choice, he can speak every language ever created, he can control the four elements, he's immune to any type of weaponry, he hypnotize any person of his choice, and he can never be told no to any question he ask, no matter if it's silly or if it's serious.