Juan is a half demon. However, he hides his demonic ancestry to escape the demons, but when a powerful weapon belonging to his mother is stolen he must venture into their realm to retrieve it.

Juan Dela Cruz is an orphan boy who was brought up in a church by Roman Catholic parish priest Father Cito, who guided him towards goodness and faith in Jesus. His devotion to Christ led Juan to refer to Jesus as "bossing" (Filipino for "boss", due to Jesus being considered as the "shepherd", or "boss", and the "flock" the followers of Jesus). One day, Father Cito is killed by a thief, and Juan ends up at Lola Belen's house in Quiapo, Manila. Unknown to him, he is half-aswang, the son of Samuel Alejandro, the Haring Aswang (King Aswang) and also the prophesied Anak ng Dilim (Child of Darkness). He is fated to rule over the Aswangs and take over the human race. However, his mother Amelia is a human and a Tagabantay (Guardian) from an ancient lineage of defenders using the Bakal na Krus (Iron Cross) to protect the humans from the Aswangs. When he's grown up, Juan joins the Kapatiran (Brotherhood), a group composed of people who seek to destroy the Aswangs. The group trains Juan into becoming the next Tagabantay. Later, the Engkantos and Diwatas aid Juan in his duties which seems to have a more important role on the continuing conflict between the aswangs and the humans.—wikipedia