Blurring the line between revenge and romantic feelings
I haven't forgotten you for a single day. Every day my thoughts... always turn on you, bastard.The person in question is obsessed. Because of some small slight, they stalk the person down, spending all of their time thinking about them. But it's not like they're in love or anything. It's just that this person has to pay for what they've done. This trope comes in a few flavors, either they realize they are in love and drop their revenge, they fail and settle for romance instead, or perhaps they succeed in their revenge and have it end tragically for the other party either having no idea what to do with the rest of their life or realizing too late that what they actually felt was love. Of course, this is not a bad thing. It makes for an interesting premise to have a love story centered around two people who are supposed to be at odds with each other. Compare with Foe Yay, which is similar but without the revenge subplot, and with more emphasis on shipping. See also The Only One Allowed to Defeat You.
Kyoko, Skip Beat!.