When Maho the commander of the Kuromorimine tankery team steps down to head to a university. It's up to sub-commander Erika to take her spot as commander. When she gets the news she doesn't believe that she can be a good leader like Maho. While she takes a walk to figure everything out she takes a stumble and fall directly on familiar person on the side of the riverbed. And when she falls on the one she rejected months ago her life is changed forever.