Tetsuo has the same fur color as their mother Lydia.
After the hybrid bear crisis, Jerome and Lydia got 6 pups: four males and two females. One of them was Tetsuo. They and their siblings were born in autumn in Futago Pass, three days after the birth of Weed's and Koyuki's pups Bellatrix, Orion, Rigel and Sirius.
When a volcano erupts in Ōu, the dogs are forced to flee. Tetsuo is too small to run fast enough and is carried by the Ōu army to safety but they pass out from the smoke and ash in the air. Jinemon Kurohabaki finds them and takes them to an abandoned mine where he locks them up. Tetsuo and the others are later released by Daisuke who acquires the key from Jinemon.
A few months have passed in Ōu when the son of Akakabuto, Monsoon, attacks the Ōu Army intending to kill them all and take back his father's land. His brother, Lenov, is crushed and killed by one of the bears. Tetsuo and their brother Akira try to help their brother but both are slashed and instantly killed by the bears.
- The dog pictured here could be either Tetsuo or Akira.
- His silver fur color isn't seen in any colored pictures but was mentioned in the story.