your information is wrong, you need to complete the game entirely, getting every piece of clothing and side quest as well as the main quest, then visit the deep forest.

you can get it at literally any time

What do I need to do to clear the game and get the Janna is a whore outfit?

No it doesn't, it triggers when you explore the alley in a certain main tale street event, regardless of what you wear

are you gonna add sex scenes or like certain people with personalitys that enjoy the exposure?

You just chose wrong,

its supposed to be invisible