I think Ban's backstory more than anything is what sold me on this series in the early part of it. I look at it now from a cynical perspective knowing just how pointless a lot of those early struggle were and how stupid the story got as time went on, but at the time I was hooked. I wanted to know more and I wanted to see how Ban's story would go from here. The second OVA is just a series of vignettes that don't really go anywhere. Mildly amusing and maybe a little but of world building but nothing particularly worthwhile there. It's just sadto go back and look at these older entries in Nanatsu Taizai's anime and see what might have been.