A soldier that Crevanille met at Fort Leinfaltz in Dulkheim. He was assigned to Crevanille's team, Black 4. Previously, he was stationed at a base in the capital of Dulkheim. He was tested there and then transferred to Fort Leinfaltz. He is a Ruin Child and stated he was treated well in the Dulkheim military because of that. Unlike Crevanille and Frayne who were also Ruin Children, Vallery was taken into the Dulkheim military while young and raised as a soldier. He is diligent in training as a fighter. He puts on a cool air but is hiding a passion. With an honest and steady personality not matching his outward appearance, he is full of ambition and reliable as a comrade.
As a member of Crevanille's team, he accompanied them on their furlough to Ribocca village to visit Dixon's wife. They also encountered a strange monster while helping villagers find an item in the forest nearby. The village was destroyed by an angel, killing all the people including Dixon's wife. After this, Vallery offered to help Crevanille in his quest to defeat the angels.
When the team returned to Fort Leinfaltz, they were assigned on a mission to escort Lumis Lichtmann back to base from Saudrick city. After they rescued Lumis from kidnappers, Lumis insisted on visiting a certain ruin nearby. They did so and found a female Ruin Child, Frayne, sleeping at the top floor. The building came under angel attack and they had to quickly take the Ruin Child and escape. The team needed to fulfill their mission of bringing Lumis to Leinfaltz but Vallery felt bad about rushing Frayne with them. He offered to take her to the laboratory at a slower pace while the others went ahead. Frayne refused at first, but Crevanille convinced her to go.
Muntzer, a Royal Guard from Valkania, attacked Fort Leinfaltz to obtain a Ruin Child because Valkania had no Ruin Children to progress in their spell research. Vallery was captured by Muntzer's troops. Muntzer, who commanded much respect in his country as a Royal Guard, convinced Vallery to join Valkania. He felt indebted to Muntzer for treating him respectfully rather than as a prisoner. He believed Valkania was working toward the good of the world, not just for its own country. Vallery was appointed as a captain in the Valkania army and ordered by Muntzer to take over Sunsail (a Marquelay village), but failed because Crevanille's group fought and defeated him. His former allies questioned why Vallery switched sides to Valkania and he claimed that Valkania was searching for a way to defeat the angels. He had found out about Dulkheim performing inhumane experiments on Ruin Children.
Some Valkanian soldiers distrusted Vallery because he wasn't Valkanian and would betray them. They suspected Vallery was a spy because he came from Dulkheim with Bryntir, and Bryntir had fled. But only Muntzer still trusted him, and Vallery fought for Valkania's sake, even battling against Crevanille.
After Muntzer was killed by Alfonse, Vallery lost his direction. He had sided with Valkania only because he believed in Muntzer's goal for peace. Some Valkanian soldiers, led by Norman, distrusted him and attempted to kill him. Vallery fled and ended up cornered in a forest north of Ordinale. Crevanille and his party rescued him and he joined them.
After Muntzer was critically wounded, he urged Vallery to leave for his own safety. The other Valkanian soldiers distrusted Vallery and would kill him. Reluctantly, Vallery left but was pursued by the Valkanian soldiers and cornered in a forest north of Ordinale. Crevanille and his party rescued him and he joined them.
Having fought on many battlefields, Vallery had slain a great number of soldiers. One of them was an Ordinale soldier whose family lived in Marquelay. The young son of that soldier hated Vallery for killing his father and wanted revenge. Vallery was downhearted about what to do but Crevanille reconciled them. Vallery apologized for slaying the boy's father, and the boy forgave him. After this, Vallery found a new motivation for fighting -- to bring an end to the war as quickly as possible.