I used to really hate him, but sweet mask turning out to be a monster struggling to hold onto his humanity totally turned that around for me. But even more than that, I love how Saitama sees right through his sweet talk and gives him a genuine reason for saying no, what's the point of all that popularity if you kill your own personality and freedom in the process? Saitama doing hero work just for fun is exactly what makes him a true hero, he's not bound by obligation or public image, he just saves people cuz he likes doing it. Also, I've said this before, but I'm pretty sure Saitama's a hero monster, and sweet mask's monsterfication just further cements this in my head.