Here is a breakdown of what makes this dynamic work, along with classic and original romantic storyline templates.
Kyo Sohma is a classic "hot-headed" tsundere. He constantly yells at Tohru, calls her an idiot, and storms off. But the "lovely" in Fruits Basket is profound. Kyo's softness is not just romantic interest; it is self-acceptance. When he finally stops running and holds Tohru, saying he wants to be with her even if his curse never breaks, it destroys the viewer emotionally. The dere becomes an act of salvation.