"Chō Mashin Eiyūden Wataru" centers on Wataru Ikusabe, a young boy who embarks on a grand adventure to save the mystical world of Sōkaizan. After discovering a portal in his school’s storage room, Wataru is transported to Sōkaizan, a realm where he is recognized as the destined hero. The world is under threat from the evil emperor Dōraku, who seeks to conquer Sōkaizan and spread his malevolent influence. Wataru learns that he must gather the legendary Mashin, powerful dragon-shaped mecha, to stand against Dōraku and restore peace.

Wataru’s journey is guided by the wise and enigmatic Shibaraku Tsurugibe, who provides counsel and assistance. Along the way, Wataru befriends a diverse group of allies, including the spirited Hinata and the loyal Kotsuru. Each Mashin Wataru encounters possesses unique abilities and is tied to a specific region of Sōkaizan. To awaken and command these Mashin, Wataru must prove his courage, wisdom, and compassion by overcoming trials and defeating Dōraku’s minions.

The narrative unfolds through a series of episodic challenges, with Wataru gradually assembling his team of Mashin and growing stronger both physically and emotionally. The stakes escalate as Dōraku’s forces grow more formidable, culminating in a climactic confrontation where Wataru must harness the full power of the Mashin to defeat the emperor and save Sōkaizan. Themes of friendship, perseverance, and self-discovery are woven throughout the story, as Wataru’s journey is as much about personal growth as it is about saving a world in peril. The series balances action, humor, and heartfelt moments, creating a compelling tale of heroism and adventure.