Ane Kitto: H na Onee-chan Irimasen ka?

Put a strand of hair inside, pour hot water, cover with futon and wait for ten minutes... Pretty much like preparing a cup ramen but it is actually the procedure for making an elder sister.
One night when Kazuya is walking back home to his apartment, he encountered a suspicious old woman. She offered him her commodity, the Ane Kit. He bought the stuff after a short sales talk. Though he is very doubtful and felt like it was just a bogus, curiosity won and he end up using the kit. And there appeared what he never really anticipated -- an Onee-chan. She would last for two weeks however.

from kaorinusantara