From Tranquil Spring: Ketain always jealous of his older sister Acukuko, which gets all the attention and feels an incredibly distant goal. Sudden change in the life of Acukuko makes Keake overestimate his relationship and his opinion about his sister. The name of this series symbolizes the relationship between Kiyoko and Atsuko. It is taken from the mathematical design and can be considered a "point of departure". This is the moment when, from the point of view of the viewer, two parallel lines are finally found. To illustrate this, think about standing on the railway tracks that continue in a straight line, as far as the eye can see; The tracks are parallel and will never meet, but in terms of the viewer, they seem to be approaching each other, the further they are,