One day, when Shouta returned home, he found an unfamiliar girl talking with his mother. The girl was 'Sachiko', the daughter of his mother's friend. Coming from the countryside, she had a modest appearance, but Shouta was excited by Sachiko's large breasts, which were noticeable even through her clothes. And so, he planned to sneakily play naughty pranks on Sachiko's voluptuous chest.
