In the peaceful village of Monja, a battered girl named Tonari appears, seeking help. She is the granddaughter of Tonkararin, the demon blacksmith on Majin Island. Tonkararin and Tonari were attacked by invaders from the demon realm but were rescued and brought to Monja Village. Meanwhile, Wataru, despite his upcoming date, rushes to Majin Island upon hearing about a crisis in Sōkaizan. There, he confronts the villains and battles their summoned demons. In a desperate moment, Tonari is taken hostage and reveals the location of the Emperor Dragon.

Wataru and his friends reach Dragon Cape. They rescue Tonari from the clutches of KinKakk and GinKakk, who were trying to extract information about the Emperor Dragon. Himiko disguises herself as Tonkararin to confuse the enemy. Wataru finds the Emperor Dragon's resting place and successfully revives it. Shoryuuko and Jyakomaru join the battle, while Wataru faces off against KinKakk. The Emperor Dragon's power strengthens their mechas, and they defeat the combined demons of Jigokushura and Onibenkei. Gendragon-sai returns to his true form, and peace is restored to Majin Island.