I'm Serious About Cultivating Immortality, so Why Did I Become a Monster?

[Mortal] [Steady] [No heroine] [Old Yin Bi] In other people's systems, it would be a big deal if a boy changes to a girl, but my system can even change species! Be a human today, a ghost tomorrow, a demon the next, and even become someone else's pet! I can be an immortal Buddha from the human race, and I can also be a great sage from the demon race! This is my, Gu Yang's, way of cultivating all kinds of dharma! ………… Who in the world doesn't want to become an immortal? Gu Yang traveled through time, went through many hardships, and was about to become a disciple of the Xuanhuo Sect. However, just as he was about to become a disciple, he was suddenly pushed into the monster pool. The bloodthirsty demon fish in the pond were hungry and thirsty, and competed with Gu Yang for food. At the critical moment, the long-awaited golden finger [Wanfa Fellow] was finally activated, and Gu Yang... Turned into a demon fish of the same style. Gu Yang: "Hello, big brother!" Demonic Fish: "... Where is my food???" [The realms of this book are: Qi training, foundation building, golden elixir, Yuanying, spiritual transformation, void refining, integration, Mahayana, transcending tribulations, and ascension. There are four small realms, namely: early stage, middle stage, late stage, and perfection.