Impression:
Would you be able to sacrifice a single life in order to save thousands? It sounds like a pretty simple question. Why not do something like that? Thousands of lives are greater than any one life. However, what if the person in charge of that decision happens to be quite close to the sacrificial lamb in question? An outside source may say that something is very simple, but everyone has a personal bias.

The distortion of reality is happening.
A loop would occur every time Alis and company failed to save the world. Alis believed that he was obtaining clues in the outside world in order to help his cause, but he could never find them after he brought them over. Well, some of those things were clues, but they were being destroyed. Dee would burn them. Why is that? Dee is the one that is causing the distortion. During the setup for the cultural festival, Dee was working on a step-ladder and she was not using it safely. She fell off of said ladder and out of an open window. Dee died and the entire class made a wish.
Stop this from ever happening and let us go back to living our normal lives from now on. -Class 3-4
Alis found a way to make this space unstable because Ai is a unique entity in this world. Unlike the other helpers, she joined class 3-4. Her vote changed the way that the cultural festival went down and this is making the space unstable. This allowed Ai to find some evidence, but Dee stepped in and told her the whole story. Along with the death, it is revealed that Dee loves Alis. She can’t stand the thought of not being needed by him, but she feels like she can’t be someone special to him. Not only does she know that he would sacrifice anything, including her, in order to rescue the class, but she has his blood on her hands.

Well, Alis basically did the same thing.
Current Opinion of the Show:
This arc is better than I ever expected. We pretty much knew the stuff about Dee probably being both dead and the cause of the distortion. Heck, it was pretty obvious that she was in love with Alis as well, but it is the little things that really add to this drama. The fact that she is haunted by the blood on her hands is pretty interesting. She felt so bad for Alis that she decided to shoot him so he would reset. That is crazy and I love it. Dee’s character is fairly interesting. She and Alis represent the two sides of a single coin. Dee wishes for safety through a stoppage.
If there is nothing on the other side of the glass, then there is nothing to hurt the fly. – Dee
On the other side, Alis wishes for progress into the unknown. There are two kinds of people in this world. I do enjoy the focus that these characters are getting because I am a big fan of this arc.

That is the look of a broken heart if I have ever seen one.
Unfortunately, everything in life comes at a price. Honestly, I don’t think that Dee shooting Alis would stop him from being able to love her. He has gone through a similar situation in which he shot all of his classmates knowing that they would be reset. No one has clean hands in this series. Even being the reason that the time distortion is the way that it is probably wouldn’t kill him. I can see a very sappy ending in which Alis recognizes the fact that Dee has been there for him throughout the years and that means a lot to him. Even though the years would be fewer in number without Dee’s interference. That is why I think that the statement Alis made about sacrificing someone for the class was a little short-sighted. I can’t imagine him saying that if he knew that Dee was the one that had to go. Could I be wrong? Of course. I am a romantic and I am making this arc into a teen drama by talking about it like this. Well, it’s not like I am stretching it too much by doing so.I guess we will find out everything in the next episode. I doubt that they would leave the arc open at the end of the season.

Enjoy that out of context please.