"Dragon Ball Movie 2: Sleeping Princess in Devil's Castle" is a 1987 anime film that expands on the early adventures of Goku and his companions. The story begins with Goku and Krillin training under Master Roshi, who assigns them a mission to rescue a sleeping princess named Lucifer from the clutches of Count Lucifer, a demon residing in Devil's Castle. The mission serves as a test of their skills and bravery, with Master Roshi promising to teach them the Kamehameha wave if they succeed.

Goku and Krillin set out on their journey, encountering various obstacles and adversaries along the way. They face Count Lucifer's minions, including a vampire, a werewolf, and a mummy, each presenting unique challenges. The duo's determination and combat skills are put to the test as they navigate the treacherous castle. Along the way, they meet a young girl named Mai, who claims to be searching for her lost brother. Mai joins them, though her true intentions remain unclear.

As they progress deeper into the castle, Goku and Krillin discover that Count Lucifer plans to use the sleeping princess Lucifer to awaken a powerful demon. The princess is under a spell, and her awakening would bring catastrophic consequences. The heroes confront Count Lucifer in a climactic battle, where Goku's strength and ingenuity prove crucial. With the help of Krillin and Mai, Goku defeats Count Lucifer and breaks the spell, saving the princess and preventing the demon's resurrection.

The film concludes with Goku and Krillin returning to Master Roshi, who acknowledges their success and begins teaching them the Kamehameha wave. The story emphasizes themes of teamwork, perseverance, and the importance of protecting others, while showcasing the early dynamics between Goku, Krillin, and their mentor. The film serves as a self-contained adventure within the larger Dragon Ball universe, offering a blend of action, humor, and fantasy that aligns with the series' tone.