1st rival of eternity is the first episode of the MBS Drama Adaptation called Sengoku BASARA Moonlight Party. It aired on July 12, 2012.
The Takeda Army of Kai prepares for their battle at Nagashino but unbeknownst to them, the Date Army of Oushuu is closing in on their rear flank. Tiger and Dragon clashed as Sanada Yukimura finds a new rival in the Chief of Oushuu, Date Masamune. Takeda Shingen acknowledges this new rivalry as something extraordinary.
In the heat of the battle of the two hotblooded young generals, a powerful adversary cuts them short of their enjoyment. A rain of arrows was repelled by Masamune but Yukimura was not too lucky as one bullet hit him in his midsection. It is none other than the Oda Army led by the Demon King Oda Nobunaga. He also brought with him his three loyal retainers Mori Ranmaru, Nōhime and Akechi Mitsuhide.
Masamune, infuriated of their interference, decides to recklessly attack Nobunaga despite Kojūrō's warnings. Nobunaga effortlessly humiliated Masamune by cutting the latter's trademark crescent moon helmet in half.
Just as when Nobunaga was about to deal the finishing blow, Shingen interposes and blocks Nobunaga's massive attack. Nobunaga then decides to fight the Old Tiger of Kai instead. Shingen unleashes his powerful earth-splitting attack but Nobunaga dodges it with relative ease and sends a fatal counterattack on Shingen. This caused everyone, especially Yukimura, to believe that Shingen was killed right at that moment.
At the Takeda Army Fortress in Kai, Yukimura laments at how he was unable to protect His Lordship. Out of gratitude for Shingen's heroic act and perhaps out of guilt as well, Masamune and Kojūrō decided to stay by the side of the Takeda Army for the time being. Masamune thought about why the Old Man Takeda would sacrifice himself for a total stranger. Kojuurou proposed the idea that Old Tiger found a new and perfect rival to help the Young Tiger mature.
Sasuke told the lamenting Yukimura that in the absence of Shingen, the latter will act as the commander of the Takeda Army. Yukimura remembered Shingen's encouragements and their constant name and punch exchanging but this did not lifted his spirits up. This infuriated Masamune who reiterated that the Old Man Takeda would probably punch the sense out of Yukimura is the latter keeps on mopping around and feeling helpless. A fistfight ensued between the two hotbloods as their loyal retainers watched in a safe distance.
While the two hotbloods are exchanging punches, a soldier of Takeda informs Sasuke that Uesugi Kenshin is approaching Kai. Two soldiers were knocked down by an assailant. Sasuke recognized her as Kasuga, a fellow ninja. Kasuga steps back and presents her Lord Kenshin to everyone. This is when Masamune and Yukimura had finally stopped their fistfight. Kenshin remarks at the awful situation of the Takeda Army and if things continue to be like that, he will have no choice but to take over.