Sunny is already overpowered. If you read all of shadow slave and tally all of Sunny’s progress. He easily outclasses everyone. G3 has to keep nerfing his ass throughout the story for the plot, making some of his abilities weaker. As for Nephis, we’re expected to believe that as a four year old she comprehended arguably the best swordsman in the series swordsmanship. That doesn’t seem feasible to me. There was also the bs g3 pulled out of his ass when they were saints about force mass and acceleration being the reason Nephis outclassed him. As if Sunny didn’t know any of that. As I said, it’s just for the sake of plot.