Just want to add something, after reading it recently again, probably for the fifth time.
I think we all wish Show can explain the entire reason about the ending, but in reality, he already did, we just probably did not pay enough attention or better yet not study ancient world history and culture. He probably was getting paid a lot to draw Undark, so to heck with Vampeerz.
When Ichika was shown by Enlil about both her and Aria life, she saw a lot of stuff. Around a hundred small panels. Most are from the past chapters, but if you pay attention, there are some new panels showing unfamiliar places or situations. For example, Pyramids. A semi ruined temple which can be a ziggarut. As it turned out in the very last chapter, it IS a ziggarut with Aria in front of it. Then Ichika has visions of Aria being a miserable beggar, with no hope and just waiting to die. Those are the info Ichika needed to understand her mission. Also, the panels are not random, there is some form of arrangement order to them. This is a mercy-kill.
Aria is around 4020 years old. Ibbi-Sin of Ur was defeated and captured by Elam around 2004 BC. That was the year Aria was born. When she met Al-Kamil later on in Georgia, she recognized and developed a relationship with her because they were both war orphans. However, war orphans can mean a lot of things, there is no indication that Aria was ever enslaved in Elam otherwise Shin would never asked her as a scapegoat queen.
A key difference between Assyria-Babylon and Elam is that Elam did not practice scape goat kings and queens. So that put Aria not in Elam. Ur and other Babylonian nearby city-states were destroyed, Ur's ziggurat was mostly gone by then, after all, the king was executed. So, she could not be in the southernmost part of Mesopotamia either. The infrastructure was gone by then.
But we saw in the last chapter there is the big panel of a large ziggurat, with Aria in front of it, reminding us of Ichika's vision. It is a temple of gods, either in Mesopotamia and Iran. That means Aria was a war refugee, may or may not be a slave from Ur (unlikely, she has no value). Iran was ruled out. That meant she was in most likely in Northern and Central Babylonia, or what we called now, Assyria. Babylon was mostly defeated by then. Assyria controlled a lot of city states in Babylon, and even later on southern Babylon. They built a lot of ziggurats for each city states that they controlled. And guess what? Assyria inherited Babylon's tradition of scape goat kings and queens. Every time a royal couple visited a city state, the royal astrologer (such as Shin) would calculate the date of bad omens, usually such as solar or lunar eclipses. The real royal couple will be ushered into a secret location while continuing their rule, while the chosen (usually slaves or people with no values) scape goat royal couple would put up an appearance in court as if they were the real rulers, even though they were essentially under house arrest and were given no information of anything, including their fate. The citizens never knew about the switch, they just assumed their kings and queens were ruling as normal. Once the bad omen has faded, the real royal couple would come back out of hiding to rule, and the scape goat couple would be sacrificed. Aria was the scape goat queen.
What the author did not record was WHO saved Aria. It could be a last-minute rescue like what happened to Kara. We don't know what happened to Shin, she either did not turn into a Lilu yet, or she was just someone resembled Shin. There was a slight facial feature difference between the two characters. We will never know. One thing for sure, just because you made someone a Lilu does not mean you are up the hierarchy of becoming the next king. Sakuya is an example. So, Shin can be made by someone else later on, including Aria. This is the only plot I wished Show will show us.
The rest of the questions I think the author has put enough clues that we all can figure them out ourselves. Al-Kamil probably is now being "jailed" in the desert. The most treasured experience between the two 14 years old couple were the kisses, not sex. Hence retaining the feeling of kisses as a way to reawaken Ichika was Ichika's personal wish before death and Enlil's granting. Enlil adores Ichika.
If you continue to read some of the illustrations done by the author even a couple of years ago, he would still draw the two of them, slightly older. One of them was explicitly stated as "a few years older", and they engaged in much more sensual and sexual activities. Not kissing, but Aria biting Ichika's ear. This is not a Lilu's thing since Aria no longer needs blood. Interestingly, "a few years older" means they are of legal age. Both of their hair grew much longer. Maybe too old for Show to draw Lolicon stuff for the two protagonists.
Can the manga's ending be better? Yes. But I think it is good enough. Just like Prism, it ends just at the right place despite of signs of being canceled.
