Just like Mona Lisa. Volume 1

"In this world, people are born without a gender. Their bodies shift toward their desired gender when they reach twelve years old. Until Hinase's eighteenth spring, they lived content without a gender. But the bubbly girl Ritsu and thoughtful boy Shiori pull Hinase in opposite directions when they both confess their feelings on the same day! Romance was never on Hinase's mind, so how can they respond? Hinase may be forced to choose a new identity...