Souichiro, a lone wolf-type angel, grew up in a single-parent household. He was happy that his father, who had worked hard, was getting remarried, but he didn't want things to get noisy. For example, like the troublesome classmate, Katou Yui. After being relentlessly pursued by Yui, whom he disliked, Souichiro returned home exhausted to find his new stepmother and her son, Yui, waiting for him!? Souichiro tries to avoid Yui, but as he interacts with him as a step-sibling, he begins to see an unexpected side of him...?