What was Kid Sojo doing in the Shokoku island?

We know he is not a native because his body exploded when he touched datenseki, so he is from Japan.

If this is the case, why is he in the island? Did the Sword Master bring a 7 years old to the battlefield and made him watch a genocide?

We know he is not a native because his body exploded when he touched datenseki, so he is from Japan.

If this is the case, why is he in the island? Did the Sword Master bring a 7 years old to the battlefield and made him watch a genocide?