Strongest☆Invincible My Sister

After yet another pervert attack by Yuuji in the morning with some help by Hatsune, Marie decides she will find out Hatsune's weakness so that she will not be able to stop her from punishing her brother. But it seems that Hatsune doesn't have a weakness. Later Kazuki finds out that Hatsune has a fever and collapsed. Kazuki thinks it is because she overworked herself in taking care of her and the household, so she decides to take care of Hatsune and the household so that her sister can get well and do what ever would make her happy.