The Hero Returns - Chapter 481

However, he did not know that he was not raising just a harmless pet, but a biological weapon secretly made by the government… a real monster.

As a former librarian, Rand felt that he had been living an ordinary life, the one that he had reclaimed unconsciously every single day.

Recently, he has been a little upset because the pet fish he accidently brought home to raised seems to have undergo some strange changes

Well, it turned into a merman.

- Description from Novelupdates

Kyo Mazuru traveled to the world of Bleach and landed in the forest of Menos Grande at the beginning.Picking up a asauchi left over from Shinigami's death, and starting with a sword, he spent hundred years in the forest of Menos Grande to survive, slashing countless hollows, and his slashing skills reached the peak, until one day, he met a man who claimed to be Mr. Aizen Sōsuke!Mr. Aizen couldn't bear him to live alone in Hueco Mundo, so he invited him out of there and brought him to Soul Society!After that, Kyo Mazuru's Shinigami career began!

For ten years, Ryn lived in quiet exile with his wife Mira, far from a world overrun by supervillains. But when the flames of chaos reignite, he’s forced to return to the battlefield, stronger and deadlier than ever.By his side is Mira, his unwavering partner—devoted, ruthless, and hiding a darkness Ryn can't see.Enemies rise, old ghosts return, and war looms on the horizon. Ryn seeks justice, while Mira seeks to protect him... even if it means drowning the world in blood.Let them come.