Susamu Nakoshi, a man disillusioned with life, meets Manabu Ito, a young medical student bored with life. To relieve his boredom Ito offers Nakoshi 700,000 yen to undergo a trepanning to see if it will unlock his sixth sense, and Nakoshi eventually agrees. However, much to his dismay and chagrin it actually succeeds, and now Nakoshi must contend with seeing homunculi, the metaphysical and symbolic representations of a person's psychological disorder. He now helps people, usually against his own will and often theirs as well, with resolving their psychological problems.