User blog comment:Jopjopjop/Volume 20 Spoilers/@comment-27528886-20160102162736/@comment-25852719-20160111061954

season 1 covers volumes 1-2

season 2 covers volumes 3-4

season 3 kinda strayed from the path of the LN story line so i would say either start from the beginning since some scenes were omitted in seasons 1 and 2 or start from volume 5 since born kinda went and did it's own thing.