Koyyukkuri is shaved by anon and then attached to Reimu's ribbon. Based on Reimu's overall appearance, she might be a pet, because she's very clean and has an umbrella, which cannot be achieved by some normal stray. Koyukkuri may be her child, and anon just tries to punish/troll her, but Reimu's expression is very easy, so there is a high chance that those ko is stray/not related to her.
Actually i don't know what meaning of the a noticable lack of yukkuri
Tag indicates that there are no yukkuri in the image, nor anything which looks like a yukkuri (such as a yukkuri face on something), nor are there any indications that yukkuri are involved.
Meaning: no yukkuri in the picture = a noticeable lack of yukkuri
I suck at Japanese but here's my best attempt: Big Reimu is saying "Yun! [Something along the lines of] Reimu is totally taking it the easiest! [Then, in smaller text:] It's no crime, not anymore, right? [Rhetorical question, she is not actually asking whether it's a crime, just inviting the listener to nod along with her]"
The ko just behind her (she ends her line with "nanoze," so, a Maricha) is asking for rub-rub, I think. The slurring is extreme and the text is small so it's hard to decipher.
The ko behind Maricha I think is just saying "enough, already!" Or "no more!," and the last one just has the sfx for rolling above it. It's probably dead.
So, the text doesn't really help explain the situation. I assume Reimu is just a cruel pet who thinks the pain of what she considers scum yukkuri behind her makes her "easier" in comparison, so she drags them behind her like a train.
(sfx for rolling)no more!rub-rub nanoze Yun! Reimu is totally taking it the easiest! It's no crime, not anymore, right? [Rhetorical question, she is not actually asking whether it's a crime, just inviting the listener to nod along with her]