Tsuzuku Ryudo, 19, is the second eldest of four brothers. He is the reincarnated Red Dragon King of the Southern Seas, commanding fire, electromagnetic energy, and nuclear power in his dragon form. As a human, he demonstrates exceptional combat prowess, strategically employing diverse attacks in confrontations.

Polite and insightful, Tsuzuku favors verbal irony and sarcasm over physical aggression, generally avoiding conflict unless compelled to protect his family. Despite this pacifism, he displays sharp tactical acumen, devising plans to aid his brothers in peril.

Within the family, Tsuzuku shares a close, advisory bond with his eldest brother Hajime. He engages in playful banter with younger brother Owaru, while jointly shielding the youngest, Amaru, and their cousin Matsuri Toba. Though attracting significant female attention at Kyowa College, he remains largely indifferent. His intellect complements his combat skills, contributing significantly to the brothers' collective efforts against adversaries like the "Four Sisters" organization and their "Bulls" allies.