Oppai Igai ga Dame Sugiru Ane

Although the protagonist doesn't have any special characteristics, his skill in home economics only, is very high. To say nothing of just cooking, his skill in doing all the household chores is unimaginable for a student. Rumor of him being a skilled housewife was spread from his friends from class. The reason for protagonist becoming like this was due to the 3 hopeless sisters who lived with him. The eldest daughter, Kanako is the homeroom teacher of the protagonist. She is adored by her students as well. However, inside the home, she lives with a sloppy figure with only wearing underwear. Not only cooking, but is hopeless with every household chores. The second daughter, Yume who is a neat and clean, kind nurse who is heavily relied upon by the patients and doctors alike in the hospital. Loves to drink alcohol. After getting drunk, approaches her younger brother in an indecent manner, taking her clothes off. The third daughter, Hinori who is the student council president. An intellectual student who has top grades and has lots of trust from her teachers. However in reality, is a very jealous person and becomes sullen if she doesn't get attention from her brother. With such bad sisters, a new problem happened during this spring. The sisters contracted a disease "Cleopatra Syndrome" which involves a love addiction and heavy dependence on their younger brother. The protagonist was told from the doctor that the only cure to this illness is "younger brother's sperm". "Can you do such things with your sister...?", while the protagonist being bewildered with thoughts like these, the 3 sisters started approaching him to take advantage of this situation. However, because of exceeding the limits of his body due to excessive self indulgence in addition to his normal life, the brother started resisting. Therefore, his sister made a proposal "You can take advantage of our breasts as much as you like." Relieving the stress accumulated from his sisters every day... Above all, being charmed by the benefit of being able to do as much as he pleases to the huge breasts of his sisters, which they show in the every day life, the protagonist accepted the proposal. But that was a strategy made by the sisters to cross the line with the brother, they liked very much! And the curtain opens with the flirting and erotic happenings of the younger brother who is being manipulated by his no-good sisters--- [Translated from website]