What's Wrong with My Sister? Is My Brother Willing to Refuse?

[Easy everyday]+[Single heroine]+[No rebirth]+[No blood relationship] Brother, I only have you... Heaven will give great responsibilities to people, so why did they give me a younger sister? I unexpectedly gained a younger sister, so I had no choice but to start a sister-raising plan. "Brother, if I affect your life, you must tell me and I will go away." "Brother, please don't leave me. Please, I only have you..." "Brother, I don't want to be your sister anymore, I like you..."