Sure it can, there are plenty of NSFW projects hosted already. Just make sure you mark your project as such, so it will display a warning before a user has access to it.
Viewing post in Can Itch.io host a web NSFW game?
If you go to “Edit Game”, and click on “Metadata”, on the bottom of the page there are two ticks:
Has sensitive content — This project is not suited for minors or the workplace
And
Show content warning — Show sensitive content warning before accessing game
For a NSFW project you probably want to check both. Make sure to explore all the available options in the “Edit Game” to describe your game as accurately as possible.