Read She's My Younger Sister, But It's Okay Manga:
“Jiyeon, why are you at my house…? What is this when you return home after being discharged from the army? An eleven-year-old sister lives in without a word. The cohabitation started without a warning was caused by a little sister like a beagle. It’s just getting dizzy, and to make matters worse, I enrolled in a university and stayed there all day, 24 hours a day&hel more.. lip;