Melody of the Mermaid: the Light of the Deep Sea

This novel is quite creative, with system rewards, super beast weapons, the ability to transform into Ultraman, etc., And red mermaid pearls as gifts. After reading the previous paragraph, I feel that all the mermaid princesses without official spouses will join the harem. I prefer single female protagonists, but I don't like harems very much. Come on, I can write a fanfic that I can think of. Very courageous too Although I write whatever comes to my mind, it is too confusing and has no logic at all. I can't stand it anymore