I would avoid some words: definitly "mature", "porn" or "sexual". All of them are going to be read the same way. Definitly avoid them, or Valve is going to pull your games from steam quite fast.
Even "erotic" might be borderline. I would think if it is a dating sim then "erotic" goes without saying. However, you could add warnings like:
"partial nudity" if the female nipple is visible (like in some CG in Loren)
"suggestive themes" and "suggestive language" if they talk about sex without showing anything
"references to drinking" (seems to be a big issue in Roommates)
"violence" may be necessary for Loren, if you add a rating
"gore" would need to be added if you show severed limbs and stuff, bucketloads of blood. I think you avoid this.
A quick research on Greenlight (3 visual novels from 3 different teams) shows that parental guidance texts are usually not used (or I just picked the 3 which do not show them

) Even though I know for sure that at least one of the novels does show "partial nudity" at least in the non-Steam-version. So on balance I would suggest to avoid these warnings unless you are required by law or steam policy.