Somewhere out there is a laid-back world with mysterious round creatures called yukkuris. They share a likeness with their master and bounce around them. While yukkuris chat perfectly well with one another, to anyone else it's just gibberish that sounds like "yuyuyuyuu," "yukkuri," or something similar.
Yukkuri Reimu is Reimu Hakurei's yukkuri, a strange little mascot of the Hakurei Shrine, waving about a tiny purification rod.
Yukkuri Marisa is none other than Marisa Kirisame's yukkuri. She's a floating head magician who carries a mini mini hakkero around and loves explaining everything. Sitting on her master's lap, Yukkuri Marisa chatted away with Yukkuri Reimu.
"Alright! Today I'm gonna explain about Reimu Hakurei and Marisa Kirisame! Reimu Hakurei, as her name suggests, is the Hakurei Shrine's shrine maiden. Some even call her the boss of resolving incidents. And then there's Marisa Kirisame. She's just a slightly odd, ordinary magician!"
"Wait, who are you even talking to?" asked Yukkuri Reimu.
"I dunno! But when all of us get together, I just start explaining stuff! That's what a Yukkuri Commentary is all about!" said Yukkuri Marisa, looking terrified for some reason.
And she wasn't the only one. The yukkuri sitting on Reimu's lap suddenly started making a fuss, leaving both Reimu and Marisa puzzled.
"They're going 'yuyuyuyu' again," sighed Reimu.
"Almost like they're actually talking, huh?" noticed Marisa.
"Or maybe they just want a snack. Here, have a rice cracker," said Reimu.
"Yukkuris really are bizarre little creatures..." remarked Reimu.
"Not even sure they count as 'creatures.' They're not familiars, that's for sure," Marisa pointed out.
They voiced their doubts about these mysterious beings that so closely resembled themselves. Hearing this, the yukkuris started having a conversation of their own.
"We don't know what we are either! If you're so curious, YOU, our so-called masters, should go look it up!" complained Yukkuri Reimu.
"Don't bother. They can't understand us anyway. And Reimu and Marisa aren't motivated enough to actually research yukkuris," explained Yukkuri Marisa.
"Gosh! Everyone's just way too laid-back..." concluded Yukkuri Reimu.
"Anyway, every day's peaceful. Neither we nor our masters will take yukkuris seriously unless some kinda incident happens," voiced Yukkuri Marisa.
"You mean, unless a huge incident occurs that affects only us yukkuris?" questioned Yukkuri Reimu.
No such thing would ever occur in this laid-back world, where all they did was lounge around on their masters' laps. Unless trouble comes rolling in from another world, nothing will change.
"And if it did happen... what would we do?"
"Fight some insane boss!"
"Build all sorts of gadgets to power up!"
Unaware that such a day was already drawing near, their baseless fantasies piled one on top of the other, crafting a tale of adventure without end.