We are brought back in time to when Yume and Mizuto were once a couple. A time when neither of them could control their nerves in what was their first ever relationship. Having already held hands and kissed before, the young couple are eager to take the next step. Spring break passes, however, with neither able to make the first move. Upon entering their third and final year of middle school, the two are regrettably put into separate classes. Alas, unable to spend as much time together as before, they both begin to grow apart.
Ah, high school. Is there any better place to start fresh after a horrible middle school relationship? Nope! Not unless your ex ends up at the same school as you and is now your stepsibling. What was supposed to be a sanctuary of peace where I could avoid ever seeing her again has become a living nightmare! Everywhere I look, I see her—in my house, in my school, in my class. There's no escape! She even claims that she's the older sibling. Like hell she is!
But I won't lose to her. After all, I'm the older brother in this new family situation. That's right, we're family now. No matter how much we may have thought we loved each other before, we saw one another's true colors and realized we weren't meant for each other. That's why even though we may keep up a buddy-buddy sibling act for the sake of our parents, things will never go back to the way they used to be.
