Yes, not necessarily for Sol and Luna but Soul definitely needed more.
I don't know, I think the few pages Sol & Luna got for their backstory was tantalizing but in the end, unsatisfying because it was underexplored. Why did they conflict with their brethren, leading to their exile? If the point of their exile was basically a learning opportunity, why weren't they taken back at the end of their own journey? Why did they just...vanish, passively becoming the Moon & Sun? Luna's conclusion was only saying "ok, you win, we'll stop tormenting you, we'd prefer that to dying, live your lives without our interference". Also, didn't Sol DIE? Andy cut him in HALF.
I wanted to see the existential and philosophical consequences of The Creator being surpassed by his Creation. I want the parallels to parenthood further explored.
Soul, oh my GOD, Soul was the most interesting of them. He was the only Rule born of Luna. He represents the intersection of the physical and the spiritual. Souls are the concept that underpins literally all of the most interesting concepts and elements in the character arcs in this story.
So I guess I'm disappointed in the author not further developing Luna & Sol, I was ALREADY hooked and wanted to see how would grow as characters. With regards to Soul, I never was hooked, just curious. He was never developed beyond being enigmatic.
Please, please PLEASE, author of UndeadXUnluck. PLEASE license the rights to your story and fictional world to a video game company. A GOOD one. Because it has absolutely crazy potential in this avenue. I'm so disappointed the anime didn't blow up, but a video game (series!) would give the potential to fully flesh out your world. Think about it!
- real-time combat system with insanely varied stacking combinations based on the negators in the mix
- groundhog day style loops with little differences in each iteration that change the world considerably.
- divergences in story based on "you might win, you might lose, and the plot changes based on the outcome" nature of the quests, rewards, and penalties - think of how "Slay the Princess" works.
- God you could even include dating sim elements, because it's the degree of connection each negator builds with each other over time that ends up fueling "heart" at the end. Imagine how it would hit the player if they had an entire romance arc which then was negated by Ragnarok, and the next loop's conditions basically making that romance impossible to replicate.