Two people who suddenly became 'siblings' due to remarriage. A quiet and inscrutable stepsister, Hikari. At first, the two of them were awkward and spoke little, but one day their distance began to change from a certain 'whisper.' The obscene language whispered softly into his ear by his sister. The brother who couldn't resist the sudden temptation. Unable to resist the temptation of his sister whispering in his ear, his reason collapses. He gets more and more hooked on his sister's sweet dirty talk.
