Very Difficult or Requiring a Lot of Effort
This page is the CodyCross answer for the clue below from Welcome to Japan, Group 564, Puzzle 2 (Ninja Training).
Question is: Very Difficult or Requiring a Lot of Effort
and the answer is: DEMANDING
Word Meaning:
DEMANDING — Requiring much endurance, strength, or patience.
Definitions from Wiktionary.