The irregulars: the journey of the three sage inheritors

a fifteen year old boy named Gen Got summoned with two others by the three great sage for a mission to unite the demons and humans for the upcoming Calamity .to prevent it from destroying their world they must make the demon lords and Heroes unite. facing lot's of challenge with Gen psychological understanding, Claude analytical intelligence and Rein kind hearth and strength, meeting various girls it's a harem with friends boy!