It is the most likely case. Your chars (so far) were all fully trained before this clan was created. So can begin as a Hiruma scout and continue as one as well, though you would be relying on different teachers, which isn't an issue, not for a while at least. The year will be 1151, less than one year after the treaty ending the war.
Lore: Nezumi will be allowed but is recommended against as I tend to avoid non humans in this setting. Jade would be fine for a Hiruma scout, because you never know.