The Outbreak of War is the 151st chapter of Shokugeki no Soma. This chapter begins the Survivor's Purge.
Erina walks out of the dorm just in time for Sōma to reveal to her father that Jōichirō Saiba is his father, to her shock. A surprised Azami questions means by this as Sōma repeats that he means what he says Jōichirō is his father.
Erina internally questions this as Takumi and the others arrive with Takumi asks about Jōichirō Saiba as Ryōko reveals that Jōichirō was not only Sōma's father but a former second seat of the elite ten at Tōtsuki. This revelation leaves the Aldini brothers and Hisako shocked and amazed at the prominence of Sōma's father.
Yūki then shows them and Erina, a picture of Jōichirō next to Sōma and the current Polar Star Residents after his last visit. Upon realizing it was all true, a horrified Erina thought back to her treatment to Sōma as she was shocked that her arch-nemesis is also the son of her idol. After processing this, she nearly fainted from the disbelief of the news. As the group tries to tend to Erina, Azami begins to ponder if it was really a coincidence that his old idol placed his son in the same school as his daughter. Both Erina and Azami are surprised that both of them know Jōichirō and questioned the other on the matter before Azami figures something out and laughs. The amused Azami begins says he thinks Jōichirō put all this into play as Sōma ignores his rambling and tells him that his revolution will be stopped before asking if he doesn't care about Polar Star.
As he prepared to depart, he told Sōma that he does in fact care but his revolution was all for the sake of correcting the "rotten culinary world" that "tainted his dear Saiba-senpai." Everyone is confused by this as Azami says that as Jōichirō's son he can bear witness to it as they continue to wonder what occurred between Jōichirō and Azami.