My Stepmom's Daughter Is My Ex

Bookish Mizuto Irido and quiet literature lover Yume Ayai once dated in middle school, drawn together by the same stories and sensibilities. As time passed, their differences widened, and they split up shortly after graduation—only to be thrown back into each other’s lives when their parents remarry, making them step-siblings under the same roof.

Neither is willing to concede the role of “older sibling,” and their awkward reunion quickly turns into a contest of pride. To settle it, they set a rule: whoever breaks the boundaries of proper sibling behavior loses, and the winner earns the right to be recognized as the elder—and to demand one request. But daily life together keeps stirring up old memories, and the feelings they thought they’d left behind begin to complicate the game.