Naruto: Pure Pathfinder!
Specially prepared slips of paper bear a customized arcane mark which allows the user to expend a fraction of their chakra (per piece) to detonate at a later time.
Individually, these detonations are painful but often not lethal (dealing 1d4 points of damage per bomb). Multiple chakra bombs used simultaneously or in rapid succession, however, can be devastating if not lethal.
Individually, each bomb costs 20 gp, and requires very little chakra to detonate.
Collectively or in rapid succession, 1d4 would require 1 chakra point to set off.