Kana Kusakabe was asked by her sister to look after her nephew while her sister went on a trip with her husband. At first, the nephew seemed well-behaved, but before she knew it, he began eyeing Kana's big tits and quickly spiraled out of control. The affection-seeking boy became obsessed with Kana's breasts, mounting her passionately as if their bodies had fused together. He invited his friends over, and they played "merging" games together, acted out spy scenarios with restraint and rape play—each innocent yet daring sexual encounter pulling Kana deeper in. She couldn't resist the boys' rough, bold actions. Finally, the nephew declared, "I get it now! When you say 'I'm coming,' it means you're feeling good, right? Take this—Mach piston!" as he pounded her chest, yet she couldn't help but climax stubbornly again and again.