"If anyone is suited for the role of "mastermind", it's Yukari." - The "official" Touhou EN Wiki

The mysterious gap youkai and sage that was among many sages who proposed and likely created the Great Hakurei Barrier that separates our world from Gensokyo. Boasting superhuman intelligence, centuries of experience and insight, Yukari is one of Gensokyo's most influential figures and most powerful youkai, in league with other powerful youkai and the elite of Gensokyo's society, and has been heavily involved in that world's numerous incidents, whether she's the cause or not.

She is directly responsible for Blake Izayoi's arrival into Gensokyo, and it was solely because she was rather intoxicated one day in 2005, right after the Phantasmagoria of Flower View incident.

However... Nothing explains why she became so interested in Kazuki Murasaki or why she decided to purposefully abduct him into Gensokyo, after she had her blunder with Blake.