[Imoru Suisou] I comforted my older sister who had her engagement called off, and it led to us staying overnight and engaging in sexual activities. [flowerswamp]

When his older sister Yui's engagement falls apart, her doting little brother steps in to comfort her—starting with an aquarium outing that feels so much like a real date she can barely believe it's happening. His shy admission that he's been watching only her all along gives way to breathless first kisses, her lush body pinning him down as they cross a line neither can uncross, and she gently takes his virginity through a sweat-slick night together. In the quiet aftermath, tangled in sheets and whispered apologies, he's simply glad his first time was with Yui-nee—while she realizes their bond may never fit inside family again.