Could you please confirm that a Mantis player gains an additional action when he uses Harumi's Battle Action to target a Berzeker, even if the Crab player delays with the Halls, as long as the zerker is in play.
Yoritomo Harumi and Halls of the Forgotten
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Harumi's additional action effect is not an effect "on" the Berserker, so it isn't delayed by Halls of the Forgotten (nor is the honor gain). If the condition is true (it should be!), meaning the Berserker is still in play, Harumi will grant you an additional action.