Something i've been wondering, what exactly is that sound effect that we see ussually accompanying those yukkuri "mon"? I mean, what is it a sound of? something soft and squishy?

too much time in the underground really hampered Flan’s eyes…

Always thought those “mon” are just the sound they made, like cats purring or something. ^^;

true. Aya yukuri did BEEP once, while others go "mon", "momon" or "ssz" so maybe they do make sounds.

Pixiv Dictionary says that it's a sound effect that's mainly used in standing upright scenes found only in Tani Takeshi's work. However, recently (at least for me), it feels like it's the sfx of how the Osa-Yukkuris communicate.

Flan thinks that any and all yukkuri are Remilia.

Cue charisma break in 5... 4... 3... 2...