That being said, quite a few novel ideas are only found in the guest stories. The existence of slime girls, goblins, good demonesses, evil angels, power runes and shrink potions, for instance. Lycalis and Viridice are also considerably more alive in the guest routes, and Margarita's inn actually feels like a meeting ground for giant and tiny alike. Also Zanna's route confronts the MC's demon-phobia in the heaven routes by showing him a paradoxical situation ('a good demoness') without resorting to magic and the hero's journey like Maryen's route.
I think that a lot of the ideas in the guest routes are sort of extra stuff that are canon, but are either going to be introduced in the future, or can't be put in the main game as it would be too bloated. Corrupted Maryen is an evil angel, and dragonesses do exist in the game world. So the bloodstone argument has some merit, as well as my theory that the MC will be a rune-powered potion-jacked chad kicking giantess ass by the end of some routes.
I never said that guest character stories
are not canon, it's not up for me to decide. What I said is that they do not set up, but based on a main story instead. I'm not sure what you meant by "Lycalis and Viridice are also considerably more alive in the guest routes", because I've never seen any story that would go further than involving a guardian of that kingdoms in it. They are mainly focused on a guest character, as they were meant to.
None of them uncover any info about Viridice or Lycalis that we couldn't know from main plot. The only thing I can remember is Zanna talking about flying monsters (wyverns?), how they can be used as food, that they attack in big packs, etc, but nothing about Keisiema for example. It's true that Margarita's Inn is a good setup for a story arc, but is not a merit of a side story. In fact, Cia's story starts there thanks to the main plot. Same goes to MC's demon-phobia. He has one because of what happened in the main story, not the other way around. Also, I'm not sure if MC is afraid of demonsses specifically. He surely was traumatized by Kendra, but I don't remember him peeing his pants when he met her again or Evalin for example, yet when a nightmare stroked him infront of Maryen (maybe she is the reason to them btw), he was afraid of her too. I think it's more like a giantess-phobia, fear of someone so big and strong compared to him even if they mean no harm. Maryen is not an angel btw.
Yes, you are right, ideas from side stories may be used on main one (I never doubted that), ther's nothing wrong about it, and yes, I must admit that bloodstone could be among those. However, if we assume that there is a chance that Maryen becomes corrupted enough to try reviving her dad, which would be pointless at that point, she might simply resort to necromancy magic instead of using runes.
