DVAJ-738 My sister lets me insert the tip up to 3cm, and our life is just on the verge of incest.

I saw my twin sister, Goba, masturbating in VR, and in a moment of impulse, I begged her to let me touch her breasts. "We're siblings! That's impossible... but maybe just a little bit..." she said, unable to contain her erotic curiosity... and finally, we came so close to penetration that we made a rule: "If we only insert the tip 3cm, it doesn't count as having sex," and we started having sex with just the tip of our penises. However, even just inserting the tip of my penis in and out of her vagina felt incredibly good, and we gradually wanted to insert it all the way in... The twin siblings' life of near-cross-the-limit tip-fucking!