Hiyori and Koharu don't fall in love over a dramatic confession. They fall in love over fishing line and silence and the way your stepdad's favorite hobby suddenly matters again when you teach it to someone. The show moves at the speed of a cast landing on water. Every episode is you sitting beside them in the boat, learning that grief and new family and belonging don't resolve cleanly, they just get easier to carry when someone's holding the rod next to you.

Three years after her father's sudden death, Hiyori Yamakawa still spends her free time fly fishing by the sea, a hobby he shared with her. Her mother now plans to remarry and has set up a dinner with her fiancé and his daughter. Nervous about it, Hiyori heads to her usual spot, where a lively girl named Koharu Minagi appears and grows curious about fly fishing. Hiyori starts teaching her, only to learn that Koharu is the stepsister she is about to gain. Slow Loop is a gentle slice of life story about fishing and two girls growing into sisters.