Repede is Yuri's faithful sidekick that sticks with him during nearly every moment in the game. Yuri has taken care of Repede since he was charged with taking care of the dogs in the unit he was with while in the Knights, which is why they have a strong bond of trust.
The pipe that Repede keeps in his mouth is a remnant of his previous owner, Captain Nylen Fedrock.
Lambert, Repede's father, was also owned by Captain Fedrock, but was killed in a battle outside of a town Fedrok and Yuri's unit was stationed. The battle involved a powerful monster, affected by the high concentration of aer in the region, that could absorb items and animals and use them in its attacks. Lambert, running ahead of Yuri, was absorbed by this monster and attacked Yuri's unit. Yuri was forced to kill Lambert in the battle. Feeling remorse for what he had done, Yuri became more attached to Repede. Captain Fedrock allowed Yuri to keep Repede. Much of Yuri and Repede's history can be seen in the animated movie Tales of Vesperia: The First Strike.
During battle, Repede will usually attack the same enemy as Yuri, but, like all other allied characters, Repede's targets can be changed using the game's "Strategy" option.
Also. Repede is known for keeping his distance from most of the other members of your team, aside from Yuri who is his main companion. Repede rejects a lot of Estelle's attempts to pet him, but when offered by the lusty Judith, he has a slight change of heart.