The Monster Kid and The Demons Sword

Kaibutsukuns father the Great Monster King suddenly complains of pain in his chest and collapses It turns out that the rival Demon King has placed a curse on him with the Demon Sword Kaibutsukun and his three companions head into enemy territory Demon Land Prince Demokin the son of the Great Demon King appears Out of curiosity he invites the monsters to the temple where the demon sword is located