Mr Fu, I Really Love You - 892 Normal Methods Cant Be Used

A con-man and policewoman that are legends of their respective professions suddenly die, then are reincarnated and return to the Tang Dynasty of ancient China as little kids.

Accepting their second chance and forced restart, they choose to use the modern knowledge and specific talents that they have in their previous lives in order to live comfortably in this new life.

- Description from Novelupdates

To be exact, the female lead is an “older sister” type, amid many beauties and handsome guys, she's no white lotus.Also, it's said that the name of this book is the same as a brand of sheep's milk powder.

“My unrequited love is over.” Compared to my perfect older brother, I, Ha Giyeon, was endlessly lacking. My first love and my last love—every single one of them were my brother’s friends. What I got in return for pouring all my affection into them were cold, violent words of rejection. Then came the thunderbolt: I wasn’t even their real son. My family, whose love I desperately sought, kicked me out of the house. Even though I scraped by doing hard labor, it didn’t feel like living. Then came the sudden car accident. Right before dying, I regretted everything and begged— That if I ever got to live again, I would never give my love to the family who scorned and discriminated against me, nor to the brothers who tormented me under the pretense of affection. I would live a life that was truly my own. And as if it were a lie, in the winter of my 17th year, Ha Giyeon returned. As Ha Giyeon began to change, so too did the family and the brothers who had once trampled him…

To treat her sick brother, she was forced to marry him in place of her cousin, who was disfigured and paralyzed. At first, their relationship was purely transactional, with neither caring much for the other. But after going through a lot together, they fell in love with each other. He doted on her deeply.She was considered an ordinary person by the world, but it was later discovered that she had multiple identities - a mysterious underground boxing champion, a highly-skilled doctor, and a mysterious and renowned composer... He also realized that their fates had been intertwined long before they met.