Good Sister in Law Forbidden Love (2015)

My friend’s girlfriend is my ex?! Unforgettable memories and an unexpected reunion with my ex-girlfriend!

Seong-cheol and his girlfriend, Hye-min, are invited to a house gathering by Seong-cheol’s friend, Ji-sang. Ji-sang warmly welcomes Seong-cheol, whom he hasn’t seen in a long time. But when he sees Hye-min, he suddenly becomes awkward — because Hye-min is actually his ex-girlfriend. After abruptly running away from home and cutting off all contact, she and Ji-sang broke up. Since then, Ji-sang has started dating his current girlfriend, So-hee. Feeling uneasy about the situation, Hye-min pulls Ji-sang aside and asks if he invited them knowing that she’s now dating Seong-cheol. Just then, So-hee overhears their conversation and tells Seong-cheol everything. The four of them sit down together to clear the air, hoping to put Hye-min and Ji-sang’s past behind them and just be friends again. But So-hee, unhappy with how things are unfolding, suddenly drops a shocking revelation.