I recommend the novel "My Water Ball Technique Has Evolved, and the School Belle Has Her Eyes on It" to you. Although the title and plot of the novel don't seem to be related to the description of your question, there is indeed a plot in which an F-class ability evolves into an E-class ability. The main character Ye Xingjue placed the F-grade Waterball Technique into the Time Space System to cultivate. Through continuous devouring and upgrading, the Waterball Technique finally evolved into the E-grade Water Lord Waterball Technique. I hope you like this fairy's recommendation. Muah ~😗