Soul-kun is a fairy-like spirit and the inseparable best friend of the young vampire Hipira. His existence began unexpectedly when Hipira assisted Salta's oldest town elder in creating a sprite within the perpetually nocturnal vampire city, forging their deep bond.

Possessing sharp intellect, Soul-kun often reads complex material aloud to Hipira. However, he displays considerable naivety in social and everyday situations. His quiet, observant demeanor provides a distinct counterbalance to Hipira's more mischievous personality.

Together, Soul-kun and Hipira experience extraordinary adventures within their supernatural world. These include disturbing Salta's residents by fabricating the arrival of morning, aiding a briar pixie against a monstrous frog prince, and encountering ravenous extraterrestrial beings following a meteorite impact on their city. Throughout these events, Soul-kun's role is defined by his unwavering loyalty as Hipira's constant companion.