God says siblings can't fall in love. If they want to be together, they must spend a hundred lifetimes as brother and sister. A hundred lifetimes later, the older sister crouches by the river, looking utterly exasperated: Why am I a man in this life...? And an only child, at that!! We're not even siblings, so why are we talking about romance?! So this is the extraordinary story of an older sister who becomes an older brother, and a younger brother who becomes a younger sister.
Well, actually, it's also a story about an older sister who becomes a hero and a younger brother who becomes a monster girl. Please don't flame me... Also, I'm not a siscon!