A teenager born with a brain condition that makes it difficult to feel emotions has his world shattered when he loses his devoted mother and grandmother and finds himself in a surprising friendship with the school bully.

Yunjae was born with a brain condition called Alexithymia that makes it hard for him to feel emotions like fear or anger. He lives with his mother and grandmother above their used bookstore is decorated with colorful post-it notes that remind him when to smile, when to say "thank you," and when to laugh. When a shocking act of random violence shatters his world, it leaves him alone and on his own. Yunjae retreats into silent isolation, until troubled teenager Gon arrives at his school and begins to bully Yunjae. After learning they have more in common than they realized, the two strike up a surprising friendship. -- adapted from jacket