Magic

Elric Melvinger. The sole heir of the prestigious magic family. Though he possessed innate talent, he had too much talent, and as such, could not learn magic. However, he then received a blessing left by his ancestors! [Eat demons.] [Swallow demons.] [Drink demons.] [Continue to keep accumulating demons within yourself, and achieve new magic!] Reach high. Reach a height so high that no one will ever reach me.

The protagonist Chan, who was looking for a part-time job after his previous company went bankrupt, coincidentally discovers a convenience store. Lured by the very high hourly wage, he decides to become a part-timer from that day. But the customers who come in seem a bit strange. Vampires, kobolds, and even succubi??