Who Ruled the Seas

I just love the anime That Time I Got Reincarnated as a Slime. Therefore, I made this anime fanfiction just for fun, trying out new imaginations. The main character is a self-insert, considering that I find self-insert fanfiction very rarely.
By the way, this is my first story and English is not my mother tongue. I only rely on Grammarly to check grammar, like in the synopsis section that you all read. So don't hesitate to correct if there are mistakes.

For a synopsis of this story. In essence, someone from our world dies and is brought into the Tensura world like a main character from the canon. Because the sea is an unexplored part of the canon story. The main protagonist is born in the sea as a sea monster and the story will begin several years before canon.
(Because of the ocean being highlighted, there will be a merfolk race to complete the story)

I didn't think my story would be good because it was intended as my writing exercise. So if there are problems, criticisms or complaints regarding my story, please tell me what I did wrong and include constructive suggestions. That would be more helpful.

nb : The cover image is the result of AI Generation