Gorou Mutsumi endured a lifelong pattern of misfortune affecting his work, education, and personal connections. Early loneliness drove him to seek solace in pets, each succumbing to tragic fates beyond his control: his goldfish Ran suffocated during a power outage, parakeet Tsubasa fell attempting flight with an injured wing, hamster Kurumi starved after escaping its cage, rabbit Mika died from neglect during his absence, turtle Ayumi was crushed during park construction, and snake Yuki perished in a shrine fire. These losses cemented his self-view as inherently unlucky.

A pivotal encounter with a fortune teller led to an enchantment placed on his cell phone. This spell manifested guardian angels – human forms of his reincarnated pets. Initial skepticism faded when he recognized shared memories of a distinctive melody he used to play for them. The angels revealed their purpose: to shield him from his persistent misfortune and external threats.

His history extends to a past existence as Sage Seijya, a being between human and animal realms. As Seijya, he stole divine powers – the Fang of the Blue Dragon, Wings of the Red Phoenix, Shell of the Black Turtle, and Armour of the White Tiger – from the Four Saint Beasts. He sealed these powers to prevent human destruction and forge a future of equal coexistence. This past act, however, drew adversaries in his current life determined to thwart the angels' mission to improve his fate.

Each guardian angel bears a phobia linked to their death: Ran suffers aquaphobia, Tsubasa acrophobia, Kurumi dreads hunger, Yuki pyrophobia, and Ayumi claustrophobia. They required Gorou's support to overcome these traumas. Their dynamic evolved into a familial bond, the angels calling each other sisters while competing for his affection. Gorou consistently showed gentleness and protectiveness, often trying to shield them despite their designated role as his guardians.

Later, Gorou pursued a career as a veterinarian, reflecting his enduring compassion for animals, persisting despite professional setbacks. The angels adapted to ordinary lives, with Yuki ascending to replace the previous goddess, overseeing human-animal balance. The narrative shifted from guardian-master dynamics toward mutual growth and familial cohesion. The Saint Beasts, once antagonists, reconciled after understanding his past motivations, aligning with his goal of harmonious coexistence.

His relationships are defined by unwavering loyalty from both the angels and redeemed Saint Beasts. Key bonds include Yuki's maternal role among the angels and her connection to Gou the Azure Dragon, along with Ayumi's reciprocal feelings toward Shin the Black Turtle. The angels' collective devotion drove them to confront their deepest fears to ensure his safety, reinforcing the theme of mutual protection and redemption across his life and past existence.