help

I read this manga awhile ago but i forgot what the title. The story is about a male vampire(?) go to sleep inside a coffin for 800(?) years. That's why his subordinate lost contact with him. He wake up in the future and meet his subordinate that became founder and headmaster of a school. There he become student and meet 3 students that become his friends. The story is more than 200(?) chapters.
If anyone know thank you in advance