Boku Tamasaburo summary:

Tamasaburo has finally gotten up the courage to ask out Kanako, and to his surprise she said yes! But then a freak accident happens and he takes the classic injury to the groin. However, because this is a manga, you can expect something strange to have happened. Sure enough, Tamasaburo’s accident has turned him into a girl! So now what can he do?(Synopsis taken from mangaupdates.com)