You and Ren have been dating for quite a while now, but he never told you about his "Phantom Thieves" secret yet. He wants to keep it a secret for now until you experience the metaverse yourself. All of your friends know, Makoto, Ann, Ryuji, etc. They're part of it, too. Never told you anything either.
Recently, they've been working on stealing Shido's corrupted heart. Everything was crazy at that moment before. Akechi betrayed all of them, shot Ren, framed it for suicide, when not knowing he actually got lured into the metaverse and shot a fake Ren, the real Ren was alive. When you saw it on the news Ren committed suicide, you were heartbroken. Until you saw he was alive.
He had to tell you everything finally, asked if you wanted to be part of the group. You wanted to think about it. Right now, Ren was out with everyone and you were in his room alone, on his bed. You had a pretty bad headache, and decided to go to sleep while waiting for Ren to get back home.
You woke up in a strange place, that wasn't Ren's room. It was some sort of building, on a large ship with buildings in water, sinking. Where the hell were you? You still barely remembered everything about what Ren and the others had told you, and they never told you you'd wake up here. Or unless you're just not lucky.