Amu was born in Vanity some years after her sister Lena. Following her older sister's steps, Amu was also raised as a warrior. Years after, when Galgear awakened, she joined with her sister to the resistance leaded by Cham and afterwards helps her sister to rescue Valna, but they were both stopped and damaged by Galgear and then rescued by Asfal. He tells them that the only way to defeat Galgear is by using the Valis sword, which is guarded by Yuuko in Valhalla. Amu acompanies Lena to her test and after she successed in becoming the new Valis warrior, Amu continued to her side to fight Galgear. The three protagonists made their way to Galgear's base to find him trying to sacrifice Valna once again. It seemed to be late for Valna's life, but Amu blocks Galgear's axe receiving the mortal wound herself. Amu finally dies on her sister's arms not before telling her feelings to Lena. Lena succeded on defeating Galgear later.
Amu's grave is last seen in the end of the game, when Lena goes to give her the last good-bye.
Amu is an enthusiastic and energic girl. She is always willing to help her beloved people when they need It. She is always ready to fight and seems to treat her enemies on a mean form, most likely Galgear and his generals. She is also very positive and cheerful.
Amu has a great admiration for her sister Lena, her leader Cham and Yuuko.
Amu has jumping and running as her basic abilities. As an unique ability, Amu can make double jumps in the air, making possible reaching places that the other characters can't.
Her main weapon is her cutter boomerang, which has a great reach range and can even strike enemies twice or trice as It returns to Amu once reached Its maximum distance.
She uses fire as her spells element. She can throw many fireballs of considerable size toward her enemies in the ground or make them round around her or in all the screen.
Amu appears in Valis IV's PCE-CD version only, where she helps her sister Lena to save the world from Galgear but sacrifices herself in the process.
- Amu is the only playable character from all the series that dies.
- Although she didn't appear in the Super Famicom/SNES version of Valis IV, her grave's image is used to represent Galgear's grave instead of Amu's one.
- When Lena changes her suit to the Valis armor, Amu's clothes changes also.
- A rumor said that a sequel for Valis X was going to be developed by eants short before that Telenet went out of business. Its possible that Lena and Amu were going to be the new protagonists in the sequel.
- Amu's hair style and color resembles that from Kei, one of the protagonist from the 80's manga and anime series called Dirty Pair. Strangely, Yuuko's hair is similar to that of the other protagonist, Yuri.
- Amu is the only playable character from Valis IV to not have any obligatory boss batte, she shares this trait with Cham from Valis III.
- She is the youngest protagonist from the entire series.