After their parents are killed in a plane crash, Ryuuichi and his younger brother Kotarou are taken in by the chairman Yuoko Morinomiya (who they call obaa-chan - meaning grandmother) with the help of her secretary (and butler) Saikawa , who they never met before, of an elite academy. Ryuuichi becomes the school daycare's new babysitter. With the help of Usaida Yushihito, Ryuuichi takes care of the babies of the teachers of the Morinomiya academy. Soon, Kamitani and Inomita joins Ryuuichi in babysitting the babies.
It's not complete yet but it's adorable.