Genmu Senki Leda

Genmu Senki Leda is a fantasy OVA from 1985 about Yohko, an Ordinary High School Student who is in love and unable to confess her feelings. Her angst inspires her to compose a piece of piano music that much to her surprise acts as a magical trigger and transports her to another world called Ashanti. There she learns that she is the legendary warrior of Leda and is tasked with bringing down the evil Master Zell who wants to use Yohko's composition for his own nefarious purposes.

This anime provides examples of:

 * Big Bad: Master Zell.
 * Blond Guys Are Evil: Zell.
 * Cannot Spit It Out: Yohko, towards her unnamed crush.
 * Chainmail Bikini: Yohko wears a blue one after she transforms. Yoni's outfit also resembles this trope, although its less armored-looking.
 * The Chosen One: There's a prophecy in Ashanti saying that whenever Leda's power is used for evil, a warrior from another world will come to protect it. In this case, that warrior is Yohko.
 * Creepy Crossdresser: Zell wears makeup, long nails, and jewelry, and it's definitely played for creepyness.
 * Face Heel Turn: Zell used to be a supporter of Leda before he betrayed his comrades and turned evil.
 * Faceless Eye: Zell has a big eyeball on his turban that's quite icky-looking.
 * Hair of Gold/Innocent Blue Eyes: Yoni, to emphasize her role as Leda's shrine maiden.
 * Have You Seen My God: Leda is said to be/have been a goddess, but in present-day Ashanti, she's mostly remembered as a legend, her shrine has fallen into ruins, and only one of her shrine maidens has survived.
 * Humongous Mecha: Yohko awakens hers in Leda's shrine. Yoni also has a clunkier less-cool-looking one.
 * Interdimensional Travel Device: Yohko's walkman.
 * Lotus Eater Machine:
 * MacGuffin: Yohko's walkman. Or more accurately, the song recorded on the tape inside the walkman.
 * Magical Girl Warrior: Yohko, in a manner similar to the Magic Knights.
 * Miko: Yoni describes herself as Leda's shrine maiden, although her outfit is completely different from real-world mikos.
 * Ominous Floating Castle: Zell lives in one, although it used to belong to Leda's supporters.
 * Redheaded Hero: Yohko, although she's not particularly fiery.
 * Save Both Worlds: Yohko's mission, since Zell is plotting to invade and conquer Earth.
 * Stuff Blowing Up: The final battle goes all out with the explosions.
 * Summon Everygirl Hero: How Yohko ends up in Ashanti. A weird case since Zell is the one who summons her (because he wants her MacGuffin), but she still serves the role of supporting La Résistance.
 * Talking Animal: Ringhum, the talking dog.
 * Transformation Sequence: Yohko gets eaten by a giant flower during hers.
 * Trapped in Another World: The plot revolves around this trope.