So, whats up with Tcho-tcho Tribe?

I would really like to get the answer to; " If Tcho-Tcho tribe is the only defending character committed to a story" ... so what is that "defending character"?

When someone is 'defending' or/and 'attacking'?

FAQ, p. 11:

"(v1.0) Attacking vs Defending
Some effects are specifically dependent
on whether a player is attacking or
defending. The active player is always
considered the attacker, and the
opponent is always considered the
defender."