The March to Being a True Emperor in a World Ruled by Beasts

In a world ruled by beasts, the last human Sanctuary promptly named "Sanctuary" is in a terrible state through a constant fight with the numerous beasts trying to take the last territory humans have. Humanities only powerhouse "Blood Emperor" is brutally injured in a fight with beasts. To protect humanity's last hope he sends a notice through the city for people under the age of 20 to head to the city center as he will find one of them to obtain his inheritance to become humans protector and leader.