Life from Zero

Yang Yue is a hero who saves the world. To do so, he appears in one fictional world after another, armed with a powerful ability: ??? (something to do with time). He also has two bodies that he can switch between. The way to switch is by kissing someone: kiss a man, and he becomes a man; kiss a woman, and he becomes a girl? Hmm, let's see whether the protagonist will choose to date women or get it on with men... (The current arc is the Re:Zero alternate world arc.)