I have "background character syndrome", where I assume I do not matter at all to the main story and am just meant to fill out the world.
I wouldn't call it a syndrome since that's a realistic way for people to think. It's not burdened by delusions of grandeur.
trouble with delusions of irrelevance is that we're closer to correct than the saps who think they're a disney protagonist.
If that's the case, I propose viewing yourself as the main character of a Slice of Life anime.
It's okay if you're not the chosen hero, it's okay to just be some guy. You can still see yourself as a protagonist in this regard so by all means, root for yourself. But it's okay if your story isn't one about a magical third act where you're isekai'd and fighting demons.
The worst delusions are the ones that have some basis in reality, because you can't reason your way out of it.
Wait wait wait, is this the Corneria with the crystals of light, or the Corneria that has furries
I have main character syndrome, but it’s where I always look out of place like the main character in a game cutscene with their custom armor
From my experience that's just what talking to strangers at a bus stop is like.
Some bloke'll come up to me and start his exposition and I'll be stuck all like, nodding along 'cos I don't want to be a dick and tell him I don't wanna talk.
Unfortunate but I feel like that’s all the socialization some people get
People keep calling me an NPC but they wont go fetch me stuff for shit pay.
I have NPC syndrome but instead of people fetching stuff for me, they seek me out to ask for my opinion on some really obscure topic
I wish people would stop coming into my tavern asking me to tell them the latest rumors, I hate gossip.
i have the "side quest character syndrome" where i'm expecting some weirdo to show up dressed in mismatched clothes to ask me to give them a fetch quest
odd individual of non-descript gender in eclectic kit
What reward you offering?
oh uhh, i can give you uhh...tea? Yeah! It's a valuable consumable! Now I really need an unicorns horn, if you could manage that. 
Oh thank you, brave hero!
Here's your reward:
Show
now if you this quest daily for 59 days in a row you'll unlock the achievement.
if you do this quest 68 more times you'll unlock the hidden romance path
I have "skull character syndrome," where I'm in the background of The Road
I have "radiant npc syndrome" where I always think that I'm coming up with unique chapters of my life but I'm actually just walking in a big circle every day.
I have cognizant NPC syndrome where every interaction puts the fear of god in me that some dude's gonna rope me into his main character syndrome or just start slaughtering everybody because he thinks his playthrough is fucked.
“Casual player syndrome” where I feel like I’m not in control and whoever is in control isn’t very good.
