The mc with love interest having complex feeling. Envy, hatred, loving, yearning, feel relate/having companion, irritated, admiring, wanna mess their lover to be, craving, want to making other party falling down or even want to break them.
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All of it or just few of that trait.
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Often only them who can predict other act, in the end Mc can tear down their love interest (or not), they starting to have feeling & grow stronger time by time.
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They are stranger, They are rival, They are also a friend, they are number one hater for each other, they are a soulmate too.