Young Sister 2 (2018)

Eun-hye is a substitute lecturer. One day she is freaked out by being stalked and calls her cousin in to live with her as her bodyguard. Kang-tae is a test repeater and he's impressed with how hard working Eun-hye is and starts feeling fond of her. One day, he drinks with his friend Tae-bum and gets drunk while talking about his cousin.