@ Kagedanji
Yeah, I meant "mediarama" instead of "diarama." Been a while since I played it. But according of the guides online, lv.42 persona is the earliest you can get it. And no: I did nothing wrong. My characters were at lv.33 at that time, so it meant I had to do a lot of grinding.
Picked the game today. That elementary school kid joined in and I finished with the 3rd level of Tartarus. Or at least I think it was the 3rd. Unless it was 4th.