A Precious Creature of Nature : Save the Beautiful Butterfly!
Rare butterflies are illegally captured. After receiving a notice from Saint Tail, Asuka Jr. sets out to discover their hidden location before the thief arrives to take them.
Aired 18/07/1996EP 36 - A Precious Creature of Nature : Save the Beautiful Butterfly!

1995
Mysterious Thief Saint Tail
Meimi Haneoka, 14, is a normal girl during the daytime, but during the night, she assumes the "position" of Saint Tail, a modern-day Robin Hood who steals from thieves and gives items back to their original owners. She is aided by her friend, Seira Mimori, a nun-in-training, and she is chased by her classmate (and soon-to-be love interest), Daiki Asuka (often called "Asuka Jr.").
(Source: Anime News Network)