Before his father's shadow faded from his memory, another scar had already painfully opened—this time, the betrayal came from an unexpected figure: Yamaguchi Samasuke.
This veteran retainer, once highly regarded by Oda Nobuhide, was entrusted with the crucial task of defending Narumi Castle, a task like a dagger at the Imagawa clan's throat. However, Nobuhide's death seemed to have shattered his former loyalty. Yamaguchi Samasuke turned to his former enemy, handing Narumi Castle over to the Imagawa clan. This was not only a loss of territory but also a blatant challenge to Nobunaga's authority.
Even more outrageous was the traitor's plot. Yamaguchi aggressively constructed fortifications in Aichi County—Kasadera Castle and Nakamura Castle sprang up, forming a solid triangular defense with Narumi Castle, guarded by his son. With the powerful Imagawa general Toyomasa Tobe commanding them, these two defenses formed an impregnable fortress.
The young and energetic Nobunaga personally led his troops directly into Narumi but suffered a setback in the initial battle. Upon hearing the news of victory, Yamaguchi Samasuke became even more rampant. He began encroaching on Oda clan territory, even building Muraki Castle on the border, like a dagger to Nobunaga's chest.
This time, Nobunaga responded with lightning speed. Muraki Castle quickly fell under the Oda army's fierce attack. However, when the attack turned to Kasadera Castle, the valiant and skilled Tobe Toyomasa brought the battle to a stalemate. After several unsuccessful assaults, the piles of corpses beneath the castle convinced Nobunaga that a sudden attack was not the best strategy.
Thus, a silent conspiracy unfolded.
A few days later, a secret letter in handwriting resembling Tobe Toyomasa's was quietly delivered to Imagawa Yoshimoto's desk. No one knew the letter's exact contents, but its subtle wording sowed the seeds of suspicion. The suspicious Imagawa Yoshimoto fell for the ruse and ordered the still-dazed Tobe Toyomasa to be recalled to Sunpu and promptly executed. Once the plague of suspicion spreads, it's difficult to contain it. Soon, the panicked Imagawa Yoshimoto turned his suspicions toward the Yamaguchi father and son. Soon after, the traitorous pair was summoned to Suruga and beheaded on charges of "treason."
Without a single soldier, using only a forged letter, Nobunaga, through the enemy's hand, eliminated three of his most pressing concerns. When the news reached Kiyosu Castle, a grim smile perhaps crossed the young lord's face—intelligence can sometimes be sharper than a sword.
By this point, Oda Nobunaga, through years of conquest, had conquered much of Owari, a territory far greater than that of his father, Nobuhide. However, the road to unification still lay ahead: the powerful Imagawa clan, eyeing them from the east, and the Ikko clan, a complex network of powerful factions within the region.
The Imagawa clan, in particular, under the leadership of its head, Imagawa Yoshimoto, dreamed of "going to Kyoto" (marching on Kyoto) and commanding the world. To achieve his ambitions, he allied himself with the Takeda clan in the west and the Hojo clan in the north, and through strategic marriage alliances, secured his rear, freeing him from further worries. Now, his greedy gaze was fixed firmly on the west.
The sky over Tōkaidō was already gathering dark clouds. A torrential rainstorm, determining the fate of the two families, was about to sweep across.