Homunculus, Genkaku Picasso Recommendations
Both series are about a loner protagonist who makes use of his ability to percieve a visual manifestation of the darkness in people's hearts to help them with the problems they don't want to face, and ultimately has to face his own troubles. Genkaku Picasso is a rather shounen approach to the subject and comparatively optimistic, whereas Homunculus brings adult subject matter and ambiguous morality into the mix.
Both manga talk about a person with supernatural powers who help others with their hidden self
Protagonist can see representation of people's hearts after a certain accident and they help people by manipulating those images. Both manga have the visuals of those hearts depicted in a creative, original and artistic way.