You Asked Me to Find a School Belle Girlfriend, So Why Did I Bring My Sister Home?

[No Rebirth, No System] [One Female Lead] [Pseudo-Incest] [Romantic Comedy] [Lighthearted Daily Life]

After the college entrance exams, she gave him the latest GS5.

He thought it was just the deep affection between siblings, never realizing that since elementary school she had known a shocking secret: they weren't related by blood!

She treated him well and kept a close watch on every girl around him.

Then, while they were living together at university, she murmured softly in a drunken haze, "I don't want to be your sister anymore."

He was stunned. Only then did he realize just how much she liked him.

Now there's just one question: what should he do about this sister he's not related to by blood?