Pieces which take multiple steps per move are probably not allowed to promote by crossing into the promotion zone and back out again: this is not explicitly stated in the rules, and chu shogi does not offer guidance here because such pieces do not promote in chu shogi, but it would contravene the usual stipulation that the move start outside and end inside the promotion zone. Another small piece of evidence is that the fire demon's burn is only calculated at the end of a turn, like promotion, and it does not apply to intermediate steps in the move. For similar reasons, "igui" or capturing probably does not allow promotion if the move begins and ends outside the promotion zone, even if it passes in and back out along the way.