Once upon a time, there was a fairy. The fairy had the ability to make flower wither. etc etc

Basically some backstory about Yuuka as a fairy. That she was hated among other fairies and was alone. Until she met a Youkai carrying a giant Scythe.

Interesting note: Yuuka was a fairy that cause flowers to decay but as a Youkai is able to cause flower to grow.

Since fairies represent aspects of Nature, does that mean that Yuuka was a Fairy of decay?...that's actually a more terrifying thought than her just being an incredibly powerful Youkai.

Yuuka backstory time...
...so far, so good.
I like where this is going.

Also,

Inukazan said:
Since fairies represent aspects of Nature, does that mean that Yuuka was a Fairy of decay?...that's actually a more terrifying thought than her just being an incredibly powerful Youkai.

This is... truth, when you think about it.
In this case, Fairy Yuuka is more Scary then Youkai Yuuka.

What was that doujinshi where Daiyousei was called a "plague fairy" by Letty?

FJH said:
What was that doujinshi where Daiyousei was called a "plague fairy" by Letty?

Because Cirno-chan is the Strongest! by Asatsuki Dou.

According to this, if Cirno does go through the same process Yuuka did, does it mean her power will change?

Control seems to be mentioned a lot, so it's not that her power changed, it just grew as her control did. Heck, it might even be an inventive way of using her existing power - reverse decay...

FJH said:
What was that doujinshi where Daiyousei was called a "plague fairy" by Letty?

I see that I wasn't the only one reminded of that.

Alignn said:
Heck, it might even be an inventive way of using her existing power - reverse decay...

You know, that's an interesting take on it, seeing how her most powerful spellcard in the story is still a destructive natured one.

We goin' back to PC-98!