Professor Yuki was an attractive professor who raked rocks at the Zen Temple.
Yuki was the ex-girlfriend of Dr. Go! and owned a piece of the photograph that has the KGB Base password on it. One of the other pieces belonged to the KGB Agent who stole her from Go!, Sascha Soychorski.
Crypto visited her at the Zen Temple disguised as a White Ninja in order to receive it. While there, Crypto attempted to reunite Yuki with Go! and there were two alternatives: Crypto reminded Yuki of the good times (reciting Haiku) and was convinced to give it another try, so she told Crypto to find the photo under one of the rocks in the Zen Temple Garden and give it to Go!; in the other, Crypto said nothing, so she sent him to find the photo and gave it to Go! as a reminder.
Yuki reappeared in the Odd Job: The Ravages of Mohgra, where she asked Crypto (who was disguised as a KGB Agent) to depose of Mohgra's Eggs in the Volcano. Yuki was seen talking to a man near a village at the bottom of the volcano and could be killed, but re-spawned the next time that Crypto visited Takoshima.