I think you mean “Lewdness”, because “Lust” only has a percentage value.
Please go to “Hideout” and look for “Rumia” to use her machine to clear the “Lewdness” value. Then Leah can drink tea to lower the percentage of “Lust”.
If you haven't met “Rumia” yet, you'll need to get an H-event from “Wharf Roach”. Be careful not to be defeated by them, or the high “Lewdness” status will lead to a game-over event.