Osananajimi no Onee-san ga Netorareta node, Boku wa Anata no Imouto to Sex shite mo Ii desu ka?

Alternative

Because my Older Childhood Friend was Taken Away from Me, is it Ok for Me to Have Sex with Her Little Sister? | 幼馴染のお姉さんが寝取られたので、僕はあなたの妹とセックスしてもいいですか？