Our boy is Kimihito Kurusu, and he seems to have accidentally become a host family while his parents are away. Oops. Some kind of paperwork screwup, no doubt.
Smith, the interspecies coordinator drops by. She's noticed that Miia is desperately in love with him.
She's here to remind him about the Prohibited Matters: any injury to the guest is strictly forbidden... and under the current interpretation of the law, deflowering counts.
Not to mention, as the first Lamia in Japan, it would be a diplomatic incident!
So hands off, buster!