Otoko Mitai Datta Osananajimi no Inu ni Natta Boku.

My childhood friend, once a tomboy, transformed into a stunning gal when we met again after years apart!! I thought we were just old pals, but a man's base nature can't resist the allure of that fully developed body. The friend who was my only companion has now become my mistress. Because she's female, the tomboy from the past has unknowingly become a sexual superior, turning this into an adventure game where you serve her.