Tatsuma and his three younger sisters; Kokoro, Hinami and Shizuku lost their parents and live together. Tatsuma never leaves his room however. He refuses to do household chores and refuses to work. Finally having enough of a freeloading brother the sisters kick him out. They can do without him. However the next month the money from their inheritance stops being deposited in the bank. Angry that he would steal money from them the oldest sister confronts him. "What have you done with our parents money!"
"We spent it a long time ago," he explains. "I'm the one who's been putting money in the bank every month." It turns out he had a programming job on his computer he did every day to support his sisters but he stopped when they threw him out. "Want money?" he asks. "Give me a blowjob." He treats his second oldest and youngest sister the same while keeping it a secret from the others as his sexual demands of them continues to grow.

All according to plan.