Saeko Yamamoto was a ski instructor who appeared in episode 038. She was the first woman to win the Moon Princess Contest at the Moonlight Course, and as such, she was also named hostess of the fourth annual contest which occurred in episode 038. Kunzite knew that "girly" Sailor Moon would be attracted to the ski contest, so he brainwashed Saeko into working for him and gave her special youma powers. Both Usagi and Rei decided to participate in the event, although Usagi did not have the ability to ski well. After all the contest participants began skiing down the slope, Saeko went after them and began using her youma powers to manipulate the course, making it much more dangerous. Soon, all of the skiers had fallen except for Rei and Usagi (who had no control over her skis). Saeko realized that one of the two girls must be Sailor Moon, so she trapped them in a large chasm from which they were unable to escape, although Yuuichirou Kumada attempted to save them.

Saeko soon transformed into the youma Blizzar and confronted the two girls and Yuuichirou, although she mistakenly believed Rei to be Sailor Moon because of her "good looks, athletic ability, and gracefulness." The two girls transformed into Sailor Senshi, and Blizzar began to attack. After a short time, Endymion appeared and stopped the battle, telling the youma that he would deal with the Sailor Senshi. He began to regain some of his memory of fighting with the Senshi, and actually attacked Blizzar with one of his roses, stunning her long enough for Sailor Moon to attack. Sailor Moon used Moon Healing Escalation to cause Blizzar to transform back into Saeko. She was not seen again during the series, but she presumably went back to her normal life after her encounter with Kunzite and the Sailor Senshi.

(Source: The Oracle :: BSSM Encyclopaedia)