Aster is a character from the game Nu: Carnival, voiced by Kashiro Futo.
Official description from the game’s website:

A familiar created by the Grand Sorcerer, Aster is a vampire who sucks blood to replenish his essence levels. As a merchant and businessman, he's been able to amass a huge fortune. His mansion located in the Royal City has become the base of operations for the clan members as they provide assistance to the kingdom.