My boyfriend, who was introduced to me by my older sister, might be having an affair with my older sister.

Julia, the receptionist at the guild, was introduced to her boyfriend by her older sister Herma, who is an adventurer. Unusually for adventurers, who are often playboys, Julia's boyfriend Rolf was a serious and honest man, and the two continued their relationship smoothly. When Julia heard that her sister was giving birth, she went to visit her, but by chance she learned that her sister's child was not her sister's husband's. And the most suspicious person was Rolf, Julia's boyfriend...