With his parents abroad, Kimihito Kurusu lived a quiet, unremarkable life alone until monster girls came crowding in! This alternate reality presents cutting-edge Japan, the first country to promote the integration of non-human species into society. After the incompetence of interspecies exchange coordinator Agent Smith leaves Kimihito as the homestay caretaker of a Lamia named Miia, the newly-minted "Darling" quickly attracts girls of various breeds, resulting in an ever-growing harem flush with eroticism and attraction. Unfortunately for him and the ladies, sexual interactions between species is forbidden by the Interspecies Exchange Act! The only loophole is through an experimental marriage provision. Kimihito's life becomes fraught with an abundance of creature-specific caveats and sensitive interspecies law as the passionate, affectionate, and lusty women hound his every move, seeking his romantic and sexual affections. With new species often appearing and events materializing out of thin air, where Kimihito and his harem go is anyone's guess! [Written by MAL Rewrite]

Morita Mayu, a high school girl. She is extremely reticent and her silence and habit of looking at people's eyes straightly sometimes cause misunderstanding. The reason behind it is not because she doesn’t like to talk nor because she has nothing to say. The reason she rarely speaks is due to the fact she thinks too much before speaking, thus losing the timing to speak altogether. But she lives a happy school life with her classmates.

The second season of Morita-san wa Mukuchi that directly follows the first.

One could say that freshman college student Tadayasu Sawaki has a wide range of vision. He has a peculiar ability that allows him to see microorganisms with the naked eye. Sawaki can see all sorts of microbes, from the fungi that cause athlete's foot to the yeast used to make alcohol, with him perceiving his little friends as cute chibi creatures. Attending an agricultural university, his talent piques the interest of numerous professors, including Professor Itsuki, who specializes in fermentation. Sawaki starts school indifferent toward his ability, choosing an agricultural school in Tokyo. However, with the help of the eccentric community around him, he slowly learns to appreciate these visible microbes and his talent. The whimsical cast of professors and classmates attending the university almost makes Sawaki seem normal despite his ability. [Written by MAL Rewrite]