Will someone explain how friendship is used in this?

Intended for beginning readers, these four stories span three seasons, feature two sheep, and illuminate one great friendship. Blanche and Otis are friends. In the fall they rake leaves (one of Blanche's favorite pastimes) from under Otis's shade tree. Later, they weather a particularly nasty storm, only to discover that the tree fell down during the night. "'My tree,' said Otis softly.... 'Things will never be the same, ' he said. . . . Blanche squeezed Otis's hoof. There was nothing more to say." At Christmas, Blanche gives Otis a baby pine tree and presents him with a pair of lawn chairs she has made from his old tree. In the spring the two friends plant the pine tree, sit in the chairs, and enjoy watching birds nest. Caple's soft illustrations depict the changing seasons and emphasize the quiet mood of the episodic plot. Blanche and Otis serve as human stand-ins; they walk on two spindly legs and go about their business purposefully and seriously. Multiple frames not only break up large chunks of text and mirror the action but also give additional clues to the ping of time, helping novice readers sequence the plot.