Relic of the Void

A contemporary college student named "Qin Bai" bought a necklace at a stall, only to discover that there was a void in the necklace! There is a demon from ancient times in the void! He stayed in the void for too long and lost track of time. He took the initiative to let "Qin Bai" devour him and continue his blood. [PS: There is only one female protagonist! The male protagonist dotes on the female protagonist and does not have any kind of confidante]