When they were sitting around the fire, I realise only Jin spoke, J-hope and even V just nodded and showed facial emotions, which could mean THIS was Jin's hallucination, and he was actually alone while he played the video of them behind him, reminiscing and replaying their time in his head, which was when he decided to go back to the place where everyone was together alive for the last time, which was the beach, and the fact he had that photo of the beach could mean they've been there together before. When Rapmon wrote "You need to survive.", it could be directed to Jin since he's the only one alive.