She says she's not my daughter, so why doesn't everyone believe her!
Six years ago, her ex-boyfriend Cassis, who broke up with her due to a diving breakup, returned as a duke. He said he was sorry for abandoning me. Who was the one who gave the breakup notice? Meanwhile, he sees her 5-year-old niece, Hanael, who she is raising instead of her sister, and begins to have strange misunderstandings.

"I had no idea. Sierra, I never thought you were raising our daughter alone..."
To make matters worse, Hanael, who was hiding, yells at Cassis to leave?

"Please don't deny it... Not our relationship, not our children."
"Bad boy! You abandoned us!"

No, he didn't abandon you. And I'm not your mom!

(Source: KakaoPage, translated)