You need to get enough affection points, to have sex with Nami on the beach.BTW, Did you unlock Hinata's room? Did you had sex with Yoruichi in club?
i have the same problem
when i go to school is only hinata, when i ask for her room number she doesn't give me, and when i go to the beach there's only Nami, if i talk with her, she's just chilling
Check rooftop, bathroom and give Hinata her book on weekends
The same thing is happening to me, I've already done all these procedures
