Rival Literature. in the Early Stage, They Were Purely Rivals, but in the Later Stage, They Gradually Fell in Love with It.

Is there any story about mortal enemies? It doesn't want to be about mutual secret love or a one-sided plot that has been planned for a long time. It should be about pure enemies in the early stage, then gradually falling in love with each other as they get along, falling in love and killing each other, similar to "Are You Sick?"