Devilman, JoJo no Kimyou na Bouken Part 1: Phantom Blood Recommendations
Jojo's Bizarre Adventure: Phantom Blood and Devilman are extremely similar story wise, both being about a young boy and their defiant friend finding out about a mysterious mask which will grant a person with a supernatural power, then later haven grown up, the main characters will have to deal with the consequences brought by the powers of the mask.
Both of these manga fall under the same demographic. They feature a main protagonist who fights against supernatural creatures (vampires in JoJo, demons in Devilman). They also contain a lot of gore and violence.