After Becoming a Koi, I Became the Nation's Lucky Fish

[Powerhouse, willful bottom vs. nonhuman, fatherly top]

Nie Chengli transmigrated from a handsome guy into a beautiful mermaid spirit, only to get killed by the person he had a flirtation with!

After finally transmigrating again, he was forced to bind himself to a sharp-tongued System. Every few days, the System would get him killed, and sometimes he even died at the hands of his mission targets. But after dying over and over, he was surprised to find that he had gone from an unlucky weakling to an all-around talent in the eyes of China's top brass...

Short version: The top occasionally makes a cameo, accompanying the bottom as he fights his way through every challenge and eventually becomes a powerhouse!