'Hikari Hamura, aka "Picasso", is the main character of the manga series.
He is a highschooler striving to become an artist, when he and his friend Chiaki end up in a helicopter accident...Chiaki prayed for Hikari to continue on in life and granted him the power to see other peoples hearts and draw them, and eventually help them out with their trouble. However If picasso decides not to help someone his arm will start to rot, and eventually he'll rot to death, by not helping people.
Picasso, granted the power to look into people hearts, saw the hearts and drew them. he bites his thumb when he draws.