A teenage brother and sister become curious about each other's bodies. The sister accidentally sees her younger brother's erect penis and, unable to resist, reaches out and touches it. This moment sparks an increasingly intimate relationship between them, and before long, they justify going further by claiming "it's not penetration if only the tip—3cm—goes in," gradually crossing into forbidden incest. *This work is an excerpt from "The Almost-Incest Life with My Sister Who Lets Me Insert Just 3cm: Chiharu Miyazawa" (Product Code: dvaj00445).