High school student Komaki Koichi, who loves cooking, is cruelly dumped by his childhood friend for being "too feminine."

Returning heartbroken to his apartment, Koichi finds popular middle school idol Hashiro Shiho sitting anxiously on his sofa. He ends up cooking for Shiho, who has become his stepsister after their parents' remarriage.

However, the result is that she tells him she wants to marry him...!?