Seven-year-old Otoka remembered his past life memories as a Japanese Salaryman after helping two chicks of a monster resembling a chicken called Niwatorisu in the forest. However, the reality was a poor large family. There was no room to raise the chicks entrusted to him by the parent Niwatorisu. Three years passed after pushing through his family's opposition. The chicks grew into splendid female Niwatorisus and began to lay precious eggs. Then, this time, his siblings started targeting those eggs...!? "I'm leaving this house already!" Ten-year-old Otoka carries out a midnight flight together with the Mofumofu strongest Niwatorisus he named Shiro-chan and Kuro-chan. In this way, a free-spirited Isekai journey begins with the cute and Mofumofu strongest Heroines——!