The introduction of the Selfish Agents who represent the Seven Deadly Sins. The Selfish Trio are the first ones who were introduced. Ira who represents the third vice and Mamo who represents the third last vice are both introduced in Episode 1. Later, Bel who represents the middle vice is introduced alone. Then Leva who represents the second vice and Gula who represents the second last vice are both introduced in Episode 23.
Despite having a similar name, similar grades and even the same theme color and Elemental Power, Rikka is not alike Reika. Avoiding to make her an Expy, she's given a different background, resulting a different personality and different skills. While Reika was the over all most competent Cure of her team and was maybe the strongest Cure after Miyuki, Rikka is definitely not the strongest and is given a supporting role in combat. The Yamato NadeshikoOjou role is given to Alice, but even here, she has not the same role as Reika or Itsuki or Karen. Because the producer has given Alice a background that gives a reason for her passive role, she's not that strong/competent as Reika or Itsuki before Alice's Character Development and she's not as strict as Karen who hasn't friends in her childhood like Alice.
Cure Ace curb-stomping Regina makes sense, as she has to defeat her within five minutes before de-transforming. And her request to the other Cures becoming stronger is justified since villains as Leva and Gula summon Jikochuus who are more troublesome than Regina. And Ace lost to the Selfish Kingdom once, so she knows there are/were much stronger villains/threats than Regina.
The last part has become contradictory in recent episodes. Ace's past has becomes more mysterious.
The villains and the Monsters of the Week are known as Jikochuu, not only because they are selfish, Leva and Gula proves that they can become Jikochuu monsters. Both of them fuse together to become a monster. They also state that is their true power.
Episode two features a Jikochuu made from a traffic signal that can literally "stop" people, turning them into statues. Okay so far, but when he turns Cure Heart and Rikka into statues, we soon realize that they're still aware and conscious. This Jikochuu had turned an entire street and a courtyard full of people into statues...And I Must Scream?
The first episode title refers to Cure Sword as the last Pretty Cure. Does that mean the others are dead?
If you mean the last of the Trump Kingdom, then it's quite likely. If you mean the last overall, then obviously no.
Judging by the flashbacks in episode 7, Cure Sword was the Trump Kingdom's sole Pretty Cure, so the former is much more likely.
Gula attacks Cure Diamond, but Cure Rosetta protects her with Rosetta Reflection. That doesn't stop him and he eats the shield. Imagine what happend if he ate Cure Diamond...
It also looks like that he has eaten people before. He also tries to eat Aguri's grandmother in Episode 27.
In episode 41, the Cures are shown to be able to fly high above the Earth's atmosphere while transformed, using their new wings. Presumably their Cure forms grant them protection from the lack of atmosphere. However, the Fridge Horror involves Cure Ace, who can only be transformed for five minutes. What would have happened if the battle in space had taken too long and she lost her transformation right there?!
When Alice and the others are six years old, Sebastian gave Rikka something that looked like a tablet, despite it was probably 2005. And Rikka knew how to use it and she analyzed Alice's whole mansion with it. It's improbable that Rikka was that intelligent.