Souta for sure! I relate with him too well, on episode six I realizef that his struggles and mine hardly differ, getting abused by siblings while working hard and I'm the youngest of my sibling and they're also girls its so fucking annoying that on Ep.6 I suddenly teared up since were the same.
The cast is pretty balanced. Everyone manages to annoys me (except Poplar) but they all have their charming points. Overall, Souma and Yamada I guess. Satou and Poplar are not far behind. Ah, also Nazuna.