Yuko Ahso is an ordinary grammar school student, but she is also the Valis.
"I defeated King Rogles of the Dark World with the Sword which was given to me by Queen Valia, but my friend Reiko died in the process..."
Yuko hasn't the slightest idea if she will be summoned to fight again.
"That voice is... uh...!? Reiko?
Why?! Reiko is Dead, isn't she..?!"
"Go and see Queen Valia, Yuko..."
Who is Megas, Yuko's new enemy? Now, the new adventure for Yuko has begun!
--from the Sega Genesis Syd of Valis instruction manual