Tensei Shitara Kozakana Datta kedo Ryuu ni Nareru Rashii node Ganbarimasu

A guy who has been reincarnated in another world remembers almost nothing about his past life. Contrary to his expectations, he becomes a small fish that wakes up in the middle of the river...
A voice in his head, calling itself "the Voice of Heaven," explains the path of his evolution, at the end of which the hero of the story will be able to become a dragon, gaining experience points and developing. The guy, having caught fire with this idea, begins hunting for the sake of raising the level. Who knew that magic, levels, and even special skills existed in this world?!
The hero begins his journey from the weakest to the strongest, starting with a small fish!