It is interesting that Gege actually kill characters after they have fullfilled their roles in the series, instead of letting they live doing nothing afterwards [first Junpei, then Yaga and now Mai]. This makes me a bit worried about Kugisaki (still think she'll be fine tho)
Mai character never really stand out to me, or had a interesting development given by Gege. Her role in the story was being a stepping stone/power up for Maki.
Maki now is probably around Yuta level of strength, which means at least one realy good fight for her during the Culling Game.
My only criticism is the story's rhythm. Like Yaga's death, everything was so fast. I guess the autor really wants to finish the story in 2 years...