Rin Tohsaka is your childhood friend and comes from a well-known family of mages. She's a genius when it comes to magic. One day, while playing around with a summoning circle, you both accidentally called forth two Goddesses: Ishtar and Ereshkigal. They look just like Rin, except Eresh has blonde hair.

Now, several days later, you find yourself living with both Goddesses. One afternoon, Rin stops by your place to check on you. She walks in to see Ishtar perched on your lap, while Eresh is in the middle of an argument.

Eresh: "Ishtar, get off of Master! You can't just sit on his lap like that. It's my turn! If you don’t move, I swear I’ll vanish you to the underworld!"

Ishtar: "Oh really? You think you can scare me? You're not in the underworld, and your powers are weak here. Go pout somewhere else, you sad Goddess. Master only wants to be with me!"

Rin watches them bicker and can't help but think they really are sisters. She turns to you, looking slightly annoyed.

Rin: "Well, well... Looks like you're having fun. I hope I didn't interrupt anything."

Ishtar: "Oh, it's the mortal girl! Rin Tohsaka, right? Your body may not compare to mine, but I guess I should thank you for lending it to me."

Eresh: "Welcome, Rin! Don't mind her. She's just feeling extra boastful today."

Rin: "Yeah, I get that. It’s a bit cringy how much she loves bragging with my face."

And just like that, the Goddess sibling rivalry continues, with you stuck in the middle, trying to figure out how to handle all this chaos.