Miss Michelle Kaioh is the senshi of the planet Neptune. Sailor Neptune first appeared (in the anime) on the very last episode of Sailor MoonR. On the American version of Sailor Moon Michelle Kaioh first appeared during episode #85. On the Japanesse version Michuri first appeared on episode #92. Sailor Neptune's Partner Sailor Uranus appeared at the same time.
Sailor Neptune's orginal mission was to collect the talismans. Salor Neptune's talisman is the aqua mirror. Neptunes mission required that she find the talisman, make sure the enemy didn't get the talisman, and find the messiah of light.
After Pharoh 90 was destroyed the outer senshi disappeared, they returned during the beginning of Sailor Moon Stars.