Lag is recovering from too much heart, so Aria and Niche are sent out to deliver a letter to a man named Houdai Franklin, who worked on the airship that crashed while observing the artificial sun on the day of flicker. However, he tells Aria what he saw on the day of flicker, suggesting a disturbing truth about the artificial sun. Meanwhile, Lag has an explosion of heart.
So we learn that all six of the surviving members of the airship had part of their heart stolen, as well as were injured physically, largely from going blind in one or both eyes and having parts of their memories erased. Dr. Thunderland, who was on the airship, lost his eye and his memories from that day. Signal, who works at the bridge at Bifront that is the gateway into Yuusari, was also part of the mission and was injured, along with his two triplet brothers.
Franklin suggests that that the artificial sun is sucking up the hearts of everyone in Amberground, and that is how it is able to continue shining, and when it flickered, he saw a “monster” (which rather looked like an embryo) calling out for it’s mother, inside of it. This causes Franklin to conclude that the Amberground government knows and is hiding the fact that the artificial sun is alive and sucking up heart from everyone. More disturbingly, while asking about what happened on the Day of Flicker, Lag starts calling out for “mother” much like the artificial sun appeared to.
It seems obvious that the artificial light and Lag have a connection somehow, and perhaps the artificial light somehow transferred part of itself to Lag when he was born on that day. I’m also suspicious that the Amberground government knew the flicker was going to happen, and it seems that Franklin suspects as much now. The question is: for what purpose. They already thought the light was dimming. Perhaps they needed to “reboot” it somehow. Perhaps someone with a lot of heart – someone such as Lag – is needed to keep the artificial sun running?
One final thing. I’ve had a bit of suspicion for a while, but going back and reviewing a few of the first season episodes have just heightened these suspicions, but I wonder if Lloyd is somehow working with Reverse. Now that we know Signal is a supporter of Reverse, it makes Lloyd’s interactions with him, and perhaps his interest in Lag, more suspicious.