From MangaHelpers:
In the past, plump and rounded women were considered the pinnacle of female beauty. Now, society, and in turn women themselves, changed the ideal female figure. This story is about a young boy and his battle against society's stigma towards healthy women. He is the guardian of plump women around the world, and he will not stop until society realizes what is true female beauty. His name is Takehaya Susanono Mikoto and he is the 150th Guardian of the "Muchi Muchi."