A job looking after monster's children... that's a 'Mamoribito (Monstersitter)'! A hundred years ago, a colossal dragon appeared out of nowhere and swallowed an entire nation. Seeking the treasure sleeping within it, people began venturing inside the dragon's body where monsters ran rampant. Arialis, a rubbish ranger who couldn't make it back to the surface from inside the dragon, ended up rescued by Lumon, who had lived inside for ages running a 'Monstersitter' business, and now she's helping look after monster children?! Whether human or monster, all children are a handful! Rookie Monstersitter Arialis's childcare × fantasy!