Yui's draw dropped when she saw the member between her older sister's legs. Lina was... a boy? Onee-chan was onii-chan?! But no -- Lina had breasts, didn't she? .... very nice ones too. Yui examined them from where she was, subconsciously aware that she was beginning to grow wet. Once she'd seen her fill, she crept away back to her own bath, where she soon began to rub between her legs, moaning quietly.