Think simple language and select terms very carefully.
A leg cramp during an initial kiss, burp accidentally, fall a sofa off, or spill wine on someone’s lap. Misunderstandings happen, too, and just how the figures work them down (or perhaps not) reflects their characters and relationship development.
I love reading well-written, interesting novels with virtually any closeness degree. As an adolescent and adult that is young I read countless steamy historical romances, but at one point I was thinking, “If we see “male member” one more time, I’m done! ”
They fit with your characters’ personalities, attitudes, and normal vocabulary if you want to use euphemisms (here’s a list), make sure.