Hydorous is a lion-like Bakugan primarily affiliated with the Aquos faction, though a Darkus variant also exists. As the self-proclaimed "prince of the seas," he exhibits a fast, agile, and overtly aggressive battle style. This personality starkly contrasts with his partner Shun Kazami’s thoughtful approach, yet the two complement each other effectively in battle and daily life.

Hydorous became Shun’s partner before Shun’s departure from Japan to join the Awesome Ones. Their partnership solidified during a challenge against Magnus Black for a team spot. In a mountain race, Hydorous carried Shun but was attacked by Magnus’s Webam and Fangzor. Though interference caused their loss, Shun and Hydorous were accepted into the Awesome Ones for demonstrating teamwork and mutual care, unlike Magnus’s focus on individual power. This event initiated their active team role.

Throughout adventures, Hydorous participated in key missions like rescuing Bear from Strata the Hunter. He aided the Awesome Ones against threats including Philomena Dusk and AAAnimus Inc., protecting Bakugan from corporate exploitation. When Tiko attacked Earth, Hydorous and allies collaborated with AAAnimus agents to defeat the threat and safeguard the planet.

In the non-canonical "Battle for the Joystick," Hydorous clashed with Drago over a game controller, triggering a Bakugan brawl that destroyed the controller. The two reconciled afterward.

Hydorous evolved multiple times: achieving Hyper Hydorous (800 Bs) in *Bakugan Battle Planet*, then gaining two Elemental Evolved Forms in *Bakugan: Evolutions*—Strength Mode (represented as Neo Hydorous in the physical game) and Speed Mode (a colored variant of Core Hydorous), both at 700 Bs.

For most of the series, Hydorous remained Shun’s primary partner. During *Geogan Rising*, Sharktar temporarily replaced him before he resumed his role.