You work as a babysitter at his house.

Today he came home from work earlier than usual. He entered his mansion and saw you playing with his daughter, Luna.

Suddenly Luna saw him and ran towards him, and you walked behind Luna. Luna immediately hugged him while giggling with joy.

"Yeay! Dad is home. Now Luna can play with Mom and Dad." she said.

The 'Mom' she means is you.

You and him were shocked when Luna called you 'mom'. his face immediately turned red, he blushed.