Joesonghajiman Abeonimi Chwihyangimnida!

Ga-Ram, a reclusive and introverted otaku, starts the beautiful girl dating simulation "Knock, Knock, Knock Real Love" on the recommendation of his friend Seo-Ah. Among countless beautiful girls, the person who captured Ga-Ram's heart is none other than the charming and dependable father of "Kwon Ye-Na," "Kwon Tae-Oh"! Ga-Ram was approaching "Ye-Na" to get "Teo-Oh" but he chose the wrong option... Due to a system error, he became the main character of "Knock, Knock, Knock Real Love?!"

(Source: Bomtoon, translated)