Hayate’s parents departed on a cruise around the world, leaving him and his three sisters Haruka, Fuyuka and Natsuki to take care of the house. He thought that these three months would pass without much problems, but his sisters decided to take advantage of the situation to draw even closer to their dear little brother.

They had once made an agreement to not make any moves on him before he became a working adult, which was reaffirmed shortly after their parents’ departure. However, Natsuki gave a daring kiss to Hayate while he was sleeping to cheer him up from the strange dreams which he had been seeing. Hayate began to see her as a woman, and this incident was seen by Haruka. Despite Natsuki’s claims of innocence, the other two sisters became increasingly impatient knowing that Natsuki was one step ahead of them. A passionate summer lies ahead for Hayate and his sisters.