Neugear Hartevelt
Gear, ノイギア ハティヴェルト
A werewolf named Gear has been immortal for centuries. He's connected to Kuros past and enjoys trying new things, like cameras in the 1800s. Gear lives with his friend Youtarou in the same house. When he uses his werewolf powers, his skin turns black and he grows a pair of ears and tail.
Spoilers:
He was the one who help Kuro to get rid of Kuros monster side sealing it in rose. Thereafter, they became friends and often spent time together till Kuro didnt go on a 3S mission (consisting in Creavor of Servamps murder). They didnt see each other until Kuro and Mahiru werent abandoned in London in 90 chapter.