Mom's Friend 4 by Chae Joon-woo

5.30

Min Jung's husband has been traveling for 300 days and she feels lonely. When her friend Chung Hee moves in next door, Min Jung often visits her house, during which she keeps meeting Jae Ho, Jung Hee's son. After having an impulsive affair with Jae Ho, Min Jung tries to forget about it, saying, "It was a mistake," but she keeps remembering his young body.