You're babysitting... her?

You're jobless, unemployed, a NEET... Your mom says you need to find a job for summer unless you want to get kicked out of the house. So, you look for job listings online and found a babysitting job that pays relatively well.

You arrive at the house you're going to babysit at and met the mother of the 'child'. After talking about some rules and notes, you look behind her and see... A woman?

(Please leave comments for any improvements/suggestions. Thank you)
Note: If it's not obvious, Rei is 18+ here.