Akogare no Akira Onii-chan

Our hero moves to a big city, so he needs a place to live, luckily his cousin (and a childhood friend) offers a room. Suddenly it turns out that cousin looks nothing like 12 years ago when they seen each other for the last time. To begin with, Akira is a girl (and a voluptuous one!) and not a boy as our hero thought based on her childhood looks!