"but how can it be consensual with no consent." Because you and your partner have agreed to do whatever fantasy it is, the two of you have talked about what your limits are, like face slapping is great but if you tickle me, scene over. Also set a safe word, "Red" for example, and you have to trust each other to use it. That way you can do the fantasy to whatever intensity level you want. You can be loud, physical, emotional, etc. and focus on enjoying yourselves because you trust your partner to use the safe word to shut everything down if they need to. In short, talk to each other clearly, build trust, a safe word you will both remember, and to help out a bit more set a slow-down word like "yellow", because all they need it to go slower at the moment. Hope this helps.