The below chapter provides a complete walkthrough for The Ghosts of Sawayama. It provides a solution to the challenges in the side quest of the game, which will allow you to complete it in the best possible way.
Summoner's candle x1
Spirit iron fragment x9
In this mission, your task is to destroy the remains of Sawayama's siege. You have to destroy three containers and three crystals. Along your path, you will have to defeat a horde of yokai, mages and guardians. It is a good idea to get lots of healing items, before the mission. After you have destroyed the last crystal, you will fight boss Oda Nobunaga. The battle has been described in the chapter entitled Bosses.