The day I finally had sex with my sister had arrived. However, she established her own rule: "Inserting only the first 3cm of the penis doesn't count as sex." Following this rule, the act of inserting just the tip into her pussy unexpectedly aroused her intensely. Awakening to pleasure, my sister gradually became driven by the desire for deeper penetration, and eventually allowed full insertion. And beyond that came creampie after creampie...!