"Mashin Eiyūden Wataru Shichi Tamashii no Ryūjinmaru" is the third installment in the "Mashin Eiyūden Wataru" series, continuing the adventures of the young hero Wataru Ikusabe. The story begins with Wataru returning to his hometown after his previous journey to the world of Sōkaizan. However, his peaceful life is disrupted when a mysterious girl named Ruruna appears, seeking his help to save her world, Ryūseikoku, from the tyrannical rule of the Demon King. Wataru, driven by his sense of justice and responsibility, agrees to assist her.

The narrative unfolds as Wataru and his companions embark on a quest to gather the seven legendary Dragon Orbs, which are essential to summoning the powerful dragon god Ryūjinmaru. Each Dragon Orb is guarded by a formidable opponent, and the group must overcome various trials and battles to retrieve them. Along the way, Wataru encounters both allies and adversaries, including familiar faces from his past adventures and new characters who play pivotal roles in the unfolding events.

The series delves into themes of courage, friendship, and the struggle between good and evil. Wataru's growth as a leader and his unwavering determination to protect others are central to the plot. The dynamic between Wataru and his companions, including the loyal dragon Shinobimaru and the enigmatic Ruruna, adds depth to the story. The antagonists, led by the Demon King, present significant challenges, and their motivations and backstories are explored as the series progresses.

As the group collects the Dragon Orbs, the stakes escalate, culminating in a climactic battle against the Demon King. The resolution of the conflict hinges on Wataru's ability to harness the power of Ryūjinmaru and unite the strengths of his friends. The series concludes with a resolution that ties together the various narrative threads, providing a satisfying end to Wataru's latest adventure while leaving room for future developments in the overarching storyline.