Oppai Igai ga Dame Sugiru Ane

The protagonist has no special traits, except his extraordinary skills in home economics. He's not just a great cook; he handles all household chores with a proficiency that's unheard of for a student. His friends call him a 'house-husband prodigy.' This stems from living with his three hopeless sisters. The eldest, Kanako, is his homeroom teacher, adored by her students. But at home, she lives in her underwear, useless at cooking or cleaning. The second sister, Yume, is a neat and caring nurse, but a heavy drinker. Once drunk, she strips and makes indecent advances toward her brother. The third, Hinori, is a top-notch student council president, but insanely jealous and sulky if she doesn't get attention from her brother. This spring, they contract 'Cleopatra Syndrome,' a love addiction that makes them dependent on their brother. The doctor says the only cure is 'brother's sperm.' 'Can you do this with your sisters...?' While the protagonist hesitates, the sisters start their assault. Overwhelmed, the brother resists. They suggest, 'You can touch our breasts as much as you want.' Tempted by the stress relief and their huge breasts displayed daily, he accepts. But it's a trap! The sisters use this to cross the line with the brother they love. Thus begins a flirtatious, erotic story of a brother manipulated by his no-good sisters.