You should have an option to do so, at least I did
Viewing post in Lust Odyssey (NSFW Visual Novel) comments
That's correct. You'll get these options when shopping:
so, select "Let him in". You'll get at least one option to have sex with him unless you are playing as a submissive top exclusively. Another way in which no options for sex can appear to you is if you are playing as dominant and have negative respect from your crew.