Chizuka Kokoro is the main heroine of Tanabuchi-kun. She is his savior ever since kindergarten. And although the Tanabuchi always dates girls that he didn't like (for some reason), Chizuka didn't bother interrupting their relationship because she had a long crush for him. And Chizuka didn't mind, because she was the main heroine.

One day when Tanabuchi broke up with another girl as usual when he didn't like it. He met a nerd, and they got hooked up. Soon later, Tanabuchi told her that he was going to get serious. And she just found out, she was no longer the heroine that Tanabuchi has. Chizuka was a fool.

So, what will Chizuka do to even get back to her position when she hasn't even confessed to him?

As going through this funny and heartbreaking sadness of this story, will Chizuka succeed? Or she's just a third wheel to Tanabuchi?