"Only the tip 3cm in, living on the edge of incest with my sister (or little sister)" series BEST! The development of "only the tip" is common, but most of the time it's an excuse by men who want to go all the way. What makes this series different is that both the man and woman think they shouldn't go all the way. They think it would become incest if they did, so they strive to only insert the glans. This is good! The cowgirl position is especially erotic! Of course, just the tip isn't enough to satisfy... so they end up penetrating deeply with a full sense of taboo!!
