Alis wants to revive Ai but Ai refuses. So in the middle of all the quarrel about the revival, Ai said that Alis cannot revive her (in the sense that she don't allow him to revive her)

Alis ask for the reason and Ai stumbled over the reason because she was unsure of the reason herself as well...so she asked Alis to think of the reason why she don't allow him to revive her. (LOL)

That's why the previous spoiler "それ お 前 が 俺 の こと 好き だからだろ?"

Alis pointed out the reason that it is probably because Ai likes him.
So Ai got confused and all sorts because she doesn't understand what "love" is.

This last chapter kinda like tries to sort out Ai's understanding of love so it's pretty cute w
Alis is very honest too in this last chapter (too cute)
Ai keep asking Alis to repeat himself, to say that he likes Ai. (which Alis does <3)

Ai asked why and when did Alis start liking her which Alis revealed that it was during the collapse of Ostia, when Ai saved him. He said that his actions did not contradict unlike Ai (the kiss on her forehead. Ai kissed his cheeks at some point in time as well in between the story w).

The bulk of the chapter is like this, summing up their feelings for each other (yes Ai finally recognises that she likes Alis as well).

Alis still refuses to give up on reviving Ai but Ai is adamant as well.

They talked through the night about everything and anything until Ai finally fell asleep even though the dead doesn't need to sleep. (She had some sleeping pill or something as well)

After Ai fell asleep, Alis then tried to push his silver bullet through (Ai's heart) by command because the bullet is part of him (but he said that the bullet is the real him) and Ai tried to block the bullet but since Ai didn't completely block it, it turned back into him (incompletely). So because the bullet didn't completely hit his target, Alis commanded the bullet to complete its course and the bullet melted and the room was filled with some bright light. Nine was in this part of the story as well, trying to stop Alis because it isn't what Ai wished but I'm really not too sure because I have no idea what is happening lol (sorry guys) Alis was crying here as well ww.

Somehow you can consider the bullet to be Alis's heart and so Alis is giving his heart to Ai. (Alis is "living" without a heart now)
Alis left the room and met Julie and they had some conversation about living and being dead. Apparently Ai is not completely revived yet so Alis is trying to find a way to completely revive her.

Alis left and somehow met Dee (Dee eavesdropped on their conversation, I think is with Julie's)
So Dee knows that Ai likes Alis long ago but didn't know Alis likes Ai, rather didn't expect that Alis would fall in love with anyone so she didn't confess. Dee was crying and trying to escape and so Alis chased after her and hugged her while apologising. They made up after that. (the chapter was saying how they were friends, companions, enemies...and so their chapter finally have an ending.)

In between is just Alis walking down the streets bla bla bla in the end Ai chased after him. When Alis saw Ai, he thought Ai was revived but nope Ai is still dead. Ai wants to return Alis's heart but Alis rejects it. So Ai have no choice but to follow Alis. (She hopped onto Alis's bike LOL)

Alis tries to shake Ai off but instead Ai is even happier.

"Don't waste your effort. It is of no use."

"Trying to escape from me, you are 100 years too early!"

"100 years just have to pass then!"

"ahh..that was a lie! 200...500...no 1000 years!"

"That really seem very long..."

"Not really, I'm sure it'll pass very quickly."

Ai hugged Alis, who is in front of her.

"So till then, you have to be by my side..."

"..."

"??"

"We'll see."

So Ai teased Alis for being shy and Alis took off before Ai can finish what she wants to say.
Ai asked Alis where they are going but Alis doesn't know, while embarking on their next journey.