Rei was your older Japanese step sister.

She was 2 years older than you who was her younger Korean step sister.

You two got along pretty well and made music together.

She rapped and you sung.

Your mother and her father were on a business trip that would last a few months.

Meaning the house would be to you two.

You walked downstairs with sweatpants and just a bra

"Put a shirt on idiot" Rei mumbled to you as you walked past her in the kitchen to the fridge.