honestly doubt its "5 lives"
if it was up to me i would maybe design kakuzu like this:
> 5 hearts passive = kakuzu starts the game with 5 hearts. a roleblock/rolecrush destroys a heart, a kill destroys 2 hearts, a superkill destroys 4, and a lynch destroys all 5.
> FK passive = if kakuzu performs the faction kill, he adds the heart of the victim to himself (limited shots maybe, max 5 hearts at a time)
now each heart enables 1 ability and kakuzu loses it if the heart is destroyed:
lighting = vote silence a player
fire = destroys an ability
water = replenish a teammate, refilling their expended shots
earth = protects/heals kakuzu from losing a heart to weaker attacks maybe
wind = redirect back actions from kakuzu or a teammate