Can the boy see ghosts with his eyes?

Anyone can see ghosts. Because ghosts are the source of evil, people are sinners, and it is normal for sinners to see the king of sinners. But when a person sees a ghost, he must get God's permission, otherwise the ghost is invisible.

Another note, ghosts remain unchanged after death, ghosts are ghosts, people are people, and people do not become ghosts. Ghosts themselves are spiritual. If we insist on who changed them, it is angels. When angels fall, they become ghosts.