Sorry, I have a question, but how can I use the Pure Knight skill? It's just that the first time I used it on a prostitute was when I went up to the next location. And after that, this skill was blocked and when I had 15 SP and click on this skill, I can only use the "cure" from the drone, but the sex skill is not. What should I do to unlock it? Although it says in the description of the skill, in order to use it, it is necessary that Eden's penis be in a state of erection, although I did not understand HOW to do it.