To be fair, the truth (what little has been revealed/confirmed so far) isn't much better.
"Actually, Kurosawa-san, I was abandoned by my shitty parents when this beautiful yet incredibly mysterious onee-san, a complete stranger, mind you,
offered to become my sugar mommy for life, despite not revealing her full name, her occupation/career, her background, her motivation for taking me in, etc."
@justforthelulz He doesn't need to give his life story. Just the fact that he is living with an older onee-chan who isn't blood related to him should be enough...
This little home-wrecker would be meddling in their business whether she was blood-related or not, to be honest. She set her sights on the boy and ain't going to hold back try and get him.
So now we're right back to square one after all his efforts at getting closer to Onee-San. Welp. Back to work, my lad.