The story of Boku Dracula-kun is relatively simple: the self-proclaimed Demon King, Kid Dracula, has awoken from a long sleep, only to discover that the dinosaur Galamoth has challenged him. Swiping his father's cape, it's then up to Kid Dracula himself to set out on a journey to destroy the monster and retake his throne.
Although not related to the actual Castlevania storyline, Galamoth, the villain of the Boku Dracula-kun series, is responsible for starting the events seen in Castlevania Judgment; this somehow created a connection. According to the Boku Dracula-kun series, Kid Dracula is 10,009 years old. In Castlevania Judgment, Galamoth sends the Time Reaper from 10,000 years in the future.