They are the original. Persona is a spin off of SMT. And I guess SMT is a spin off of the original Megami Tensei?

Each one has its own story, although there are some references between them. Some of the end game choices lead to or create the realities that other games exist in.

They tend to have a bit of a different tone compared to persona. But, ultimately, you’re still collecting and fighting with demons/personas/whatever.

When you spend the night with your friend and his older brother wears his boxers around the house.