Kimihito Kurusu

Kurusu Kimihito is a "volunteer" for the "Cultural Exchange Between Species Bill", he was given a Lamia named Miia to take care of. After spending some time together, Miia fell in love with him. He was later given a Harpy named Papi as well, and then he ran into Centorea. Both of whom proclaimed their love for him. Later on he gained two more girls, Suu and Mero

Personality
Kurusu is a gentle person and incredibly selfless, often going out of his way to make others happy. For example when Miia arrived at his house, he went through great lengths to ensure she was comfortable, even going as far as to remodel certain parts of his home for her.

In addition, while at one point he stood in the way to defends a couple who were harassing Miia, so that the she would not be violating the laws against conflict between species, later on he punched one of  them for further harassment, getting himself into trouble rather than have Miia deported. Ms. Smith resolved the situation for them afterwards.

Skills and Traits
He has demonstrated ability to both take and survive startling amount of damage from any of the Monster Girls.

Plot
Miia is presented to him as part of the "Cultural Exchange Between Species Bill" by Sumike. While she stayed at his home, he was very kind to her and put much effort into making sure she was happy, to the point of remodeling many parts of his home for her.

As time passed, Miia eventually fell in love with him, although Kurusu felt the same way, there was a law in the exchange program that prohibits intimacy between humans and beast creatures. Violating this law would result in Kurusu being arrested and Miia being deported. This doesn't stop Miia from making advances on him whenever she get's the chance.

Later on he was to given a Harpy named Papi as well, but she had run away from Ms. Smith on their way over, but she kidnapped/befriended him and eventually fell for him as well. After this he ran into Centoria and helped her catch a thief and protected her from a (non-)lethal strike, resulting in her proclaiming her love for him.

Kimihito has recently been made into the guinea pig of a new amendment to the exchange program, which allows inter-species marriages, presumably rendering the rule invalid. Ms. Smith introduces the inter-species marriage addendum. Unfortunately, this happens on the night of a Full Moon which awakens a monster girl's more primal instincts, resulting in Kurusu spending the whole night trying to avoid them all.

Trivia

 * A running gag throughout the series is that whenever the girls overuse their strength/powers, Kurusu ends up getting hurt by accident.
 * In an extra chapter, Kurusu reveals he has a leg fetish; however, this is presumably to avoid the question asked by the girls about his fetish, and therefore is not completely trustworthy.
 * He is apparently independently wealthy, as he lives alone in good-sized house and is able to support four monster girls at once.
 * All the girls (except for Suu) have a nickname for him, Miia, Papi, Centorea, and Meroune call him "darling", "husband", "master", and "sir", respectively. Even Ms.Smith calls him "darling" too, albeit because she finds it amusing.
 * Kimihito knows of Miia's fantasies about him, and remarks on them whenever she thinks of a new one.