Many fan works have recently depicted Yuuka as a bit of a sadist, often being dominant over Alice Margatroid or Tenshi Hinanawi. Yuuka's conversation with Shikieiki in her scenario also suggests that she may be a sadist since she admits she likes to "tease" others daily.
In other fan works Yuuka is portrayed as an insane and bloodthirsty youkai, who kills with a pleasant smile on her face.
Many fans in Japan refer to Yuuka as the "Ultimate Sadistic Creature" (アルティメットサディスティッククリーチャー), or U.S.C. for short.
Yuuka's very low speed (focused and normal) in PoFV and MS has become a small running gag among some folks. There's even a comic in which Aya teases Yuuka with "Speed over Power" while flying circles around her, with Yuuka blasting away to no avail. This even applies to her performance in fangames such as Touhoumon and Touhou Mother in which she has very low speed, but high power.
She also loves pummeling Wriggle Nightbug to show her love to her.
In her character description in Phantasmagoria of Flower View, ZUN called Yuuka "Youkai Moé". This caught on with Western fans, who often call her this to show affection.
Yuuka's appearance as the stage six boss of Lotus Land Story and as playable in Mystic Square and Kioh Gyoku is called "Pants Yuuka" by many Western fans, due to her pants.
Her appearance in pajamas in the fifth stage of LLS is called "PJs Yuuka" by the same fans.
Yuuka's LLS st. 6 and KOG appearances is called "Long-Haired (Pants) Yuuka" and fans wish for this Yuuka to return.
KOG Yuuka is called "Wings Yuuka" due to her wings
Japanese fans seems to compare her with Hikage from the game Senran Kagura, as both having similar looks and personality.
Yuuka is known to be a motivational speaker, her most famous quote being "wen day is dark alway rember happy day."