Hiyori likes to spend her times alone fly fishing. One day, a very energetic girl named Koharu tries to jump into the cold ocean in front of Hiyori and she stops her. This ends up being the beginning of their very unique relationship.
The girls work on summer homework and Futaba comes over. She's nervous about telling her friend that she likes fishing, so they come up with a plan to see if she should tell her friend or not. Later on, the girls go fly fishing at a mountain stream.
Koharu tries to convince her dad to let her go on a fishing and camping trip with just Koharu and Koi, which causes a disagreement in the family, and results in Koharu and Hiyori running away from home.