I think you need to offer Ori a swimming, and after this action Ori will offer you a BJ
I'm sorry, but it's not like that, you need to have enough hearts and be Ori's "partner", then you have to "chat" with him/her. There is a chance that Ori invites you to go to the lake and then you need Continuing the story of that event
I was close. I always give Ori for my main love. But anyway related to the lake
