Eriri thinks she is very lucky, because she has a wonderful childhood friend. Ever since they were little, he has helped her bathe, wash and put on her clothes, comb her hair, cook for her, wake her up, go to class with her, learn to draw with her, and sleep beside her. They even once wore the same skirt. After such a huge debt of gratitude, it would be a little unreasonable not to marry him.
Besides, he took care of her when they were children, so there should be nothing wrong with her returning the favor now that she has grown up, right? But a grown-up girl can't just take care of any boy she likes, so the young lady Eriri has "reluctantly" decided to confess to her childhood friend and marry him as soon as they graduate from high school. After all, it's only natural for a wife to take care of her husband, isn't it?
It's not that she's in a hurry. She just wants to do her part to help solve the declining birth rate in Japan. And it's not that she's afraid some wicked woman will snatch away the little cabbage she's set her sights on. She just wants to repay her childhood friend for taking care of her as soon as possible.
But before graduation arrives, several wicked women with designs on her childhood friend appear at his side. Even his adopted younger sister, who shares his surname, Shiina Mashiro, is thinking about how to send him off to Germany. This gives Eriri a massive headache. If she had a choice, she'd rather something else got bigger.
And so, the cabbage-guarding battle for Eriri alone begins!
