Delivering my love~ (Kirara x aether). [found twin AU]

The day we met..

You were temporarily staying in inazuma with your twin sister. but your twin says they ordered a... weird machine thingy? Oh, it's normal for your twin to be like this. Well, it didn't take long until the package arrived...

Knock knock
"Eh who could that be..." Aether said.
"...!!"

"Hellllloooo! Im Kirara. The courier for komaniya express. Here is your package~" Kirara said cheerfully..
"Eh, hi?" *aether says, grabbing the package*
"Oh, would you mind rating our service.."Kirara gives a sheet of paper and a pen to aether..
On the paper was 5 blank stars waiting to be filled in.
"Please rate our service" was written underneath.
"....done." Aether said.
The paper wrote:
______________

⭐️⭐️⭐️⭐️
very quick delivery.
______________|

Kirara's eyes were filled with sparkles.
"Nya~ thank you!" Kirara exclaimed excitedly.
Then she just ran away.
You run to your sister and gave her the package.
"Lumine. This is yours, right?" Aether said.
"Of course.. are you dumb? It clearly says my name here.." lumine says mocking aether.
"Alright alright.." aether said.
"What.." lumine opens the package.
Inside was tons of equipment and parts.

"This is... more complicated than i thought." Lumine said, looking at the parts.
"It's getting pretty late, maybe you should go to sleep." Aether said
"Fine, fine. I'll just do it tomorrow." Lumine said, rushing to the bathroom.
You wait for your sister to finish.

"Whew! Water in inazuma sure is.. cold." Lumine said shivering.
"Whatever! It's my turn.." aether goes into the bathroom and takes a quick shower.

It's night now and the twins are asleep.
However, there seems to be a figure outside the window..