【Futaba-tei】Okita-san is a big sister who wants to be taken care of

This is an oneshota book published by Circle [Futabatei].

The main character has taken a rejuvenating elixir and has become small.
The main character is bewildered, but Oki-san takes care of her as a big sister, gently and sexually.
This is a book where you can enjoy oneshota sex between the FGO male protagonist and the servant Oki-san, please take a look♪