The Tosa Inu dog, also referred to as a Japanese Mastiff and Tosa Ken, is a fighter dog breed. Native to Tosa, a former province and city in Shikoku Island lying on Japan’s southern coast, the Tosa Inu was developed by Japanese breeders. Tosa Inu breeders in Japan developed the breed by crossing the dog with other Japanese dogs like the Shikoku breed.
Tosa breeders also crossbred the dog with various European breeds, including the bulldog, German pointers, and Great Danes. The chief aim of the breeders was to rear the Tosa dogs as incredibly powerful and aggressive fighting dogs. Nevertheless, with many countries, including Japan, outlawing and forbidding dog fighting, the Tosa dogs were gradually adapted to be reared and trained as family dogs.
Since almost all dog breeds have a natural affinity towards humans and bond perfectly with humans, you can train any dog to be a loyal family dog. Additionally, almost all dog breeds naturally tend to bond perfectly with humans. You can train any dog to be loyal to your family. However, coaching a Tosa dog to become a devoted family dog could be remarkably challenging, especially if you start late.
Therefore you must obedience training from a very early phase, i.e. when the dog is a 3-4-month-old puppy.