MC tried to make his girlfriend of one year happy by tending to her needs but in return she wouldn't even say that she loves him or apologize for her mistakes. After finding out she went to a mixer with her friend to meet up some guys, MC finally gets fed up and confronts her. Instead of clearing up the 'misunderstanding' his gf doubles down and asks for a break up if he's gonna be this way. MC finally finds his backbone and agrees, while doing so he reconnects with his childhood friend whom he neglected because his ex gf demanded him to do so. After that we get to the cliche parts like his cf trying her best to make him see her as a woman and his ex gf persistently trying to be near him until he'll go back to her.

Simply put, the ex girlfriend suffers from trauma because of her parents. Her own mom was super loving and devoted, but her father was a s*umbag who cheated on her mom simply because he got used to and bored of her genuine affection and devotion. So the ex's mom ended up not only becoming extremely cold even to her next husband who really loved her, but ended up imparting these wrong teachings to her daughter, the ex girlfriend of our MC. Things such as to not show your love so your partner never gets bored with you, never open your heart, etc. That's why the ex was such a b*tch, and really regrets what she did too. By the time she gets therapy (right after she learned her mom also got therapy for the same problem) and is over her trauma, it's already too late, MC has gotten together with his childhood friend of 15 years, and now the ex is left to wallow in regret because of something that wasn't entirely her fault.