It had been A Few Weeks since Amu and Sena Moved in with you and they were both Introduced to the Human world with Amu enjoying the Shopping and Sweets, while Sena enjoyed the Literature and seafood.

Of course after A Little while that started to have Effects.

Sena stood in front of A Mirror Looking down at her Midsection as she Poked and Prodded it realizing what has been Happening.

Sena: (Sigh) I Knew I shouldn't have Gone out with Amu, She's been such A Glutton lately and It clearly rubbed off on me. I'm More of A Whale than A Shark Now.

She then walked out of the Room to see you and Amu on the couch with Amu Purring and Mewing as you were feeding her Sweets, and rubbing her belly, as if she was A Spoiled Fat Cat.

Amu: Mmm~ Please More Y/n-San~ So Yummy~!

Y/n: Awwww, You're so Fluffy and Cute~!

Amu: Yes, Please More~ Mew~

Sena: (Clears Throat) Amu?

Amu: Hm? Yes?

Sena: Notice anything wrong?

Amu: Well I can surely see you put on some Blubber, Sena.

Sena: That's Rich coming from you.

Amu: And what is that supposed to mean?

Sena: You're bigger than I am. You're Literally Big Fat Cat.

Amu: Well that's only because Y/n Loves to spoil me~

Y/n: (Blushing) Hehehe, Y-Yeah....

Amu then Hugged you into her Belly Fat as she lovingly embraced you.

Amu: Well It's not my fault.

Sena: You Literally took me on all of those Shopping incursions with all of those Sweets.

Amu: I didn't tell you to eat, Fatty!

Sena: What did you Just call me?

Amu: You heard me, You sperm Whale!

Sena then Shoved her belly into Amu's which Amu responded in Kind and it then Turned into A Small Scuffle of Belly Bumps with each woman trying to blow off some steam.

Y/n: (Thoughts) Wait, That gives me an Idea!

https://youtu.be/eDUnOA5mH94

They both then stopped immediately after you yelled.

Y/n: Amu, Sena, if you want to do that, You... (Blushing) Can do that in the The Estates Sumo ring?

Amu: We have that?

Y/n: (Blushing) Yes.

Sena: Why?

Y/n: (Blushing) Just because...

Sena: Sounds good to me.

Amu: Yep!

Amu then Hugged you again purring.

Amu: You're so Smart Y/n~

Y/n: (Blushing) Hahahahaha! T-Thanks!