What I loved the most about the arc was how the core of touma's character remained despite him losing his memories with both his current self and his pre lost memory self being driven by the simple act of wanting to protect index. https://twitter.com/SquiIliam_/status/1347966496576860160
It also did a good job depiciting how self torn touma was with what would his pre lost memory self do and what his current self should do. made up for some of the best moments in the arc.
The series continues to distinguish itself among other anime/manga with it's power system.its incredibly well thought out and explored. It also acts as vehicle for themes of the story rather than simply being a conflict creator.
The arc also had some really layered thematic exploration. A very great and tragic deception of heroism through izzard and himegami.Their backstories were really heartwrenching and I think both contrast touma really well. I was also suprised by how explicitly violent this volume-
Was, some really brutal stuff lol.