Seiso na Aniyome wa Ore Dake no Inran Niku Onaho

"Stealing my brother's wife! Secretary taming!" The protagonist, Kiryuu Shinji, was the second son of a company president. Shinji has never got along with his arrogant brother who is the heir to their company, and so he cut his ties to them. However, when their company is on the verge of bankruptcy, Eiichi shamelessly demanded that his brother loan him some money. Unable to put up with his brother's arrogance, Shinji resolved to take revenge on him, saying that he'll loan him money if he offered a collateral consisting of his wife, who Shinji has loved since childhood, and secretary, who belittled Shinji together with Eiichi. The fate that awaits the sisters as a living onahole is... [Translated from Getchu]