The episode of the new season is a filler and it also has been used as a recap of what has happened for the past three seasons and there isn't much in the episode that I can say as there isn't much to take note about.
The new opening and ending were good, the opening is full of spoilers just like its past openings and the opening makes me even more excited for the next week's episode where Overhual finally re-appear as we got to see did get to see him in season 3 and as we see how evil he is. As for the ending, it shows Eri when she was a baby and how she grew up to the point before her parents 'death'. It was a good ending as we getting to see more about her past, and as far as I can remember not much is seen about her past even in the manga and bits of it, as she herself can't remember at all as she was still very young back then. The episode has a couple of funny scenes and it makes it light-hearted just before this arc takes a darker turn and how helpless Eri is against 'Overhaul'. I will not have a rating for this episode. They're also a few changes have been made, the title card scene in the opening and the preview has both been change and it is kind of refreshing but it will take some time of people to get used to the look.
Rating: 8/10