For what purpose does Gon mistreat a butterfly in the novel, Almond?

Gon hurts the insect in order to attempt teaching Yunjae how to feel what someone else is feeling. Though the test does not help Yunjae experience the same pain as the butterfly, it does teach him about Gon's incredible capacity for empathy. After killing the bug, Gon weeps, and storms out, embarrassed by his emotional display.