Theory#9: Nova didn't die.
Nova may not have died in the events of ASG1. It's known that Nova's Glaive transformation and "death" scene is showed. When a Glaive shatters and falls to the ground, that enemy is dead. However, this scene is completely missing from the fight. This can be interpreted as Nova surviving the battle against Gunvolt. He may have left Sumeragi as well considering the top brass believe him to be dead in ASG2.
For a while, everything seemed serene, peaceful even. Gunvolt was finally able to relax, well, not entirely. He had lost Joule and Lumen, in body but not spirit. This was a major loss still, one that would possibly never be recovered. He wouldn't say it, but they could feel it. GV would miss seeing Joule's smiling face, talking with her, and all the warm hugs he would get after a long day of work.
"I wish I could do more for you than just sing, GV." Lumen pouted.
"You do Lumen, you always have." Gunvolt assured.
"I bet you can't name anything other than sing." Lumen rebuked.
"You always made sure that I was patched up when I came back from work. You wanted to cook for me. There's so long a list really that I just can't name them all." Gunvolt answered.
"You're just lying to spare my feelings is all." Lumen sighed.
"No, that's not-" But Gunvolt found himself talking to thin air.
He wanted to apologize for all the mistakes he made in the past. But his tired mind simply wouldn't allow him to stay awake any longer. Between all of the allegations and accusations coming from QUILL, it was obvious they all blamed Gunvolt for the imminent shutdown of the company. It took all of GV's remaining energy to move himself to bed. The following morning, he awoke and decided to make pancakes. It wasn't until he was flipping the third on that he realized he placed it on a separate plate. A plate that would no longer be used unless two guests were in the house. Gunvolt knew that he wouldn't be receiving company for quite some time. Since she was the second oldest, Moniqa was in charge from then on out. It was difficult for her to deal with, especially without prior instruction. After Kamishiro's destruction, another QUILL member was sent to Japan from China. It was an Adept by the name of Xiao Wu with an unknown Septima. He was scheduled to visit Gunvolt that morning and discuss the future plans for QUILL and its affiliates. Upon remembering that detail, Gunvolt decided he would make a second stack of pancakes.
"I miss those, the smell, the taste. It was like eating a light, fluffy cloud." Lumen lamented.
"I know you do Lumen, but look on the bright side." Gunvolt commented.
"What bright side is there!? Nova may still be out there for all we know!" Lumen protested.
"That's impossible, he died, we saw it." Gunvolt reminded.
"No, we didn't. We always saw the Glaives fizzle into nothing and teleport upwards before right? Then we saw them shatter and turn into a pile of ash on the ground when they actually died. And after we tried to kill Elise the first time she let the second one loose. She may have been the reason the others were resurrected. Nova even had her work for him to do that. Maybe she revived him too after that." Lumen elucidated.
Gunvolt didn't think about that, and he felt stupid for it. He knew there was going to be a long talk later. The phone rang right after and he answered it.
"Moniqa? What are you doing calling me? Aren't you up to your eyes in paperwork right now?" Gunvolt remembered.
"I have some free time right now. Can we talk at your place?" Moniqa replied.
"Sure, I'm just making pancakes." Gunvolt confirmed.
"I'll bring Zeno by too, he'll definitely want to see you." Moniqa added.
"Okay, I have to let you go now, the pancakes are burning." Gunvolt stated before ending the call.
He returned to making breakfast as Lumen hummed a tune. From the way the tempo was, Gunvolt knew it was reincarnation. The song used to revive him, to save him from the brink of death so many times. But he wondered, just how many times could that be done before he lucked out. A few minutes later, a knock on the door rought him out of his thoughts. Gunvolt opened the door to see Zeno and Moniqa standing there with Xiao behind them.
"You're right on time, I just finished making breakfast." Gunvolt greeted happily as everyone entered.
GV was happy in that moment, but sad as well. He was relieved there was enough seats at the table for everyone. Although, it also reminded him that there was no one to grab an extra seat for.
"That reminds me, Lumen had an idea that I thought we should discuss." Gunvolt informed as he poured glasses of milk for everyone.
Decades later, the conversation was brought up again by Gunvolt.
"So, what you're saying is that may have been him, still alive? As in he never died?" Kirin inqueried.
Gunvolt nodded.
"I told you this ages ago!" Lumen fumed.
"Huh? You did?" Kirin wondered.
"I told him that Nova's Glaive didn't disappear! It's possible that it essentially held a part of his soul." Lumen theorized.
"That could be. I was looking at some data on the Glaives earlier in the database. Apparently, some reports have been made that an Adept's Septima can exist without the soul. And you did tell me earlier that Nova's Septima was so strong he could use it without a Glaive. And that an Adept's soul can exist beyond death which is known when their Septima is still active." Kirin remembered.
"Looks like we're going to be here a while." Gunvolt muttered before sitting on his dog bed.