Alba Meira

A work colleague of the protagonist's father.
For a month he's freeloading at her house.
He's surprisingly gentlemanly and familial and often helps out with the housework.
He was kind to the protagonist at their first meeting and offers to talk if she ever has any worries.
He has a younger twin brother named Soiree, they have a really strong brotherly bond.
It seems Alba came to Japan for something more than just business however...