In order to perfect his fighting skills, Jack goes on a gasshuku, but nothing could prepare him for the punishing warrior training camp - the climax of which is to enter into the Way of Fire, a terrifying ritual which burns away evil.
To prepare for the selection trials for the upcoming Circle of Three, Jack and friends take part in the annual gasshuku, held in Koya-san, located two days south of Kyoto. A total of fifteen students and three sensei (Kyuzo, Yamada and Hosokawa) were allowed to participate.
On the last day of the training camp, Sensei Hosokawa tells the students to prepare themselves for the Way of Fire. The next day, everyone enters the cemetery of Okunoin Temple, which houses the graves of samurai warriors and lords who died for Japan.
Sensei Yamada then explains the concept of the Heart Sutra, the best known of the Buddhist scriptures, to the students, demonstrating its effects by placing his hand right above a candle flame and suffering no injuries. This was merely a taste of what was to come, however, as the real Way of Fire presented itself after he tosses the candle onto an enormous woodpile behind him, causing it and the surrounding area to burst into flames.
Jack unwittingly volunteers himself for this final test, and almost gets burned to death, when Sensei Yamada tells him to "focus on where you want to go, not what you fear," bringing himself back to a meditative state, completing the Way of Fire successfully.
As everyone prepared to make their way back from the graveyard, three ninja (all of which were the Sensei in disguise) ambushed them, and Jack realized that it could be the doing of Dragon Eye. Splitting up, Jack, Akiko, Yamato and Emi confront one of the ninja, ending with Jack successfully immobilizing him with a gunner's knot to bind his wrists.
But that ninja managed to right himself up, forcing the quartet to flee, when suddenly Yamato spots another ninja on the scene - whom Jack recognized as Dragon Eye himself.
After a brief scuffle, Jack manages to knock the infamous ninja into the swamp, but not before he had the chance to use his poisoned tanto on Emi. Akiko, recognizing the symptoms of the venom, identifies it as a Sleeper type poison, one that paralyzes and suffocates the victim.
Akiko then reveals that there is a cure to Emi's condition - haki-jo maru, a flowering cactus whos blossom was said to counter any type of poison. The catch is that it is located on Mount Haku, and that it has recently erupted, making their journey potentially hazardous. After convincing Sensei Yamada to let them go, Jack and friends set off, knowing that Emi will die by nightfall if they fail.
Along the way Jack questions Akiko's knowledge on the shinobi world, like her knowledge of poisions, to which Akiko replies that the Sleeper was the same posion that killed Masamoto Tenno a couple years earlier.
Journeying on, Saburo and Yamato left the team, both suffering from the effects of the mountain's thin air and noxious fumes. After some additional difficulties, Jack and Akiko successfully accquire the haki-jo maru flower, just as the volcano erupted.
Outrunning the lava by plunging himself into a lake, Jack makes his way back to his friends, who then deliver the antidote to Sensei Yamada, who makes the cure. Emi awakes, as Jack and Akiko recall Dragon Eye's assault. They agree that the next time they wont be so lucky, and the only cure to that ninja was his death.
- The Way of Fire is an actual ceremony performed by the Buddhist Shingon sect in Japan to mark the coming of spring.
- Koya-san and Mount Haku's locations were brought together closer for the purpose of this story, when in real life they are located on opposite sides in Japan.
- Yori mentions about the events that occured during this book in the Ring of Sky, when he uses the Heart Sutra to escape a burning house.