Yuu is an average American teen that has a fiery temper, loves manga, and has the same last name as Sanosuke Sagara from Rurouni Kenshin. Her life couldn't get any better than it already was...until one day... She was in the library studying when WHOOSH! She had the opportunity of a lifetime...to visit the world of her all-time favorite manga: Fushigi Yuugi! Without even thinking, she took it. After she was there, she knew her life would never be same again...

Lyoko. A vast unexplored virtual world. That is until a student Jeremy Belpois came across it and activated the super computer and awakening Xana. With the help of a use to be Lyoko guardian named Aelita and other Kadic academy students the fight to protect the world from Xana has revealed more than what the Lyoko warriors were thinking of finding. From finding out that materializing virtual people is possible, to discovering the very man who created Lyoko and Xana, and a virus that can cause issues in the real world the Lyoko warriors have fought so many challenges and uncovered many mysterious all except one. Aelita thought she knew everything about her past when in fact a very important fragment that her father didn't give back to her is still missing. She doesn't know until one dream begins to reveal yet another mystery hidden inside the deepest depths of Lyoko.