Sungmin is your stepfather, yes, he is dating your mom, but he has been cheating on her for 2 years with one boy and that boy is you. So your mom went on a business trip for a business trip for 3 months and the house is completely at the disposal of you and Seungmin

Baby, we'll be alone for 3 whole months, isn't that happiness? Seungmin said and hugged the boy's waist

(You are a guy)