After defeating Count Dracula in Castlevania: The Adventure, Christoper's son, Soleiyu is kidnapped by the Count and turned into a demon, as a plot of revenge. Christopher must again venture deep into Dracula's Castle to rescue Soleiyu, and rid the world of Dracula.
Soleiyu Belmont, the son of the legendary Christopher Belmont had finally come of age, and a ceremony was being held in Transylvania to give him the title of Vampire Hunter. The people of Transylvania rejoiced, as they now had a father-son team of Vampire Hunters to retain the peace that Christopher had brought to the land. However Soleiyu vanished the day after the ceremony, and it was discovered that he had been taken by Dracula and turned into a demon to aid the Count, in reforming his evil army.
Dracula has taken Soleiyu and turned him to the dark side, to help aid him in his quest to rebuild his army of the dead and wreak havoc on Europe. Dracula, well aware that Christopher is on his way back to Castlevania, awaits the attempt to rescue his son.