How Did the Pure Little Sister I Picked Up Turn into a Chaste Young Master?

[A mostly cozy, sweet story + sharing a rental apartment + older woman/younger man romance + mutual salvation]

[Chatty, gossipy, adorable girl & mute, scheming young master]

When Du Ruo was six, she found a little child in the mountains. The child had fair, clean skin and an especially beautiful pair of fox eyes. Someone that pretty had to be a girl!

The little sister was not only beautiful but clever, too. Sadly, she couldn't speak. After starting college, she refused to live in the dorms no matter what.

The friends she usually hung out with were all men. Du Ruo was afraid some bad man would lure her little sister away, so she rented a studio near campus and moved in with her.

But before long, she noticed some strange things about her little sister.

She deliberately kept her distance while sleeping, never hung her underwear out to dry, and strongly resisted wearing skirts...

Even so, none of it changed how much she loved her little sister.

Whenever she was in danger, her little sister would beat up the bad guys, then pull her into an embrace to comfort her.

Gradually, she realized she had developed an unhealthy dependence on and affection for her little sister. She even wanted to keep her all to herself.

She began avoiding her little sister, trying to date men to shake off these strange feelings.

Fu Yanli was poisoned and rendered mute, then abandoned in a mountain village at the age of three. Later, Du Ruo raised him as a girl for over a decade.

He should have hated Du Ruo, but then he watched her go through one boyfriend after another and finally couldn't hold back. "Sis, your taste in men is awful. Why not take a look at me?"

Du Ruo stammered, "L-Look at you? I don't like girls!"

Fu Yanli laughed in exasperation. "After all these years, you still haven't figured out my secret?"

Du Ruo thought it over, then asked, "You don't have feelings for me, do you? You absolutely can't. You're my little sister!"

Fu Yanli undid his clothes. "Take a good look. I've never been your little sister."

P.S. The male lead is called Du Heng at first and is mute. He recovers later.