The Archfiend Tapir becomes more powerful than the party expects. Can Gintoki and the Leukocyte King put aside their differences to defeat it together?
The Archfiend Tapir, thanks to having total control of Tama's systems, has taken on Tama's appearance. This causes the Leukocyte King to be incapable of attacking him and the virus laughs at his failure. Until Gintoki kicks him in the face and continues to stomp on him, ignoring everything the virus says, adding that he never listens to archfiend speeches during games. The King angrily kicks Gintoki into the Archfiend and stomps on him while indirectly hurting the virus, hypocritically reminding his 'twin' that hurting the Archfiend hurts Tama, too. The two start to fight each other again with the Archfiend concluding that these "heroes" were too heartless to care what happens to Tama. The Archfiend decides to take on the appearance of the King's father, who was defeated and adsorbed by the head Tapir. Instead the entire Yorozuya kicks and stomps on him before he reveals his new face, their justification being their boredom with the cliched "the final boss is your father" route and, in Shinpachi's case, due to no longer having Tama's face. Their constant kicking leads to the Archfiend's throne falling out of the main system and resulting in the Tapir Boss being disconnected (He was connected by a plug from his behind). The Leukocyte King realizes that this was now their chance to defeat the virus since Tama will now be unaffected.
The four rush at him but the Archfiend blows them back into the wall. He reminds them that he absorbed the highly advanced technology Tama wields and evolved beyond a normal virus. He transforms into a giant winged demon and calls himself a god. Gintoki mocks his godhood and he, along with Shinpachi and Kagura demand that he leaves Tama. The trio start to attack but during their wordy exchange, Kagura became a pixel figure. Gintoki struggles to understand how a computer virus affected a living person and the Archfiend fires a blast at them. Gintoki appears fine but Shinpachi ends up half transformed, with the change steadily consuming him. Gintoki panics at the state of his friends just to sense another blast heading his way. He is saved by the King and the doppelgangers are forced to retreat, leaving the transformed children behind along with being chased by the Archfiend. The King accepts that the Archfiend has evolved to the point where he can control all viruses and can affect living things as well as programs. Gintoki abruptly pauses before looking in his pants and despairs. It seems Gintoki was hit by the pixel beam to his crotch and is now on borrowed time before he becomes a pixel person.
The King tells Gintoki to remain while he goes to confront the Tapir. He reiterates that he alone should die to protect Tama since that was his sole purpose. He also didn't want his master to be sad if the Yorozuya are killed. He is Gintoki's substitute after all. Remembering Tama's pleas to protect the King and forget her, Gintoki tells him about Tama's request and his refusal. He chastises the program for thinking so little of himself to push his responsibilities on Gintoki; the King may be Gintoki's copy, but they are unable to live each other's lives and they are both their own person. He reminds the stunned King that Tama considers him her precious friend so never think about dying or calling himself a substitute again. The Archfiend then burst through the wall as Gintoki finishes that they should both survive and have a drink as "brothers". The Leukocyte King agrees.
The Archfiend declares that he will defeat them and take over everything. The doppelgangers in turn declare that they will defeat him. The evolved virus fires a powerful blast, that to his surprise, becomes counteracted with the 'twins' combined blast. The virus adds more energy, both pushing them back and pixelating both their bodies. Gintoki grows worried that they were losing but the King tells him to go. While the Archfiend was distracted, Gintoki can attack him from behind and kill him. The King himself couldn't move due to his entire leg become a pixel. Gintoki tells him not to break their promise and the King answers that he won't; after all he is Sakata Gintoki. The two give a fist bump and Gintoki breaks off running towards the virus. The Leukocyte King is quickly overcome by the Archfiend's blast, his weapon even breaking. He physically holds back the blast, thinking about his purpose that thanks to finding friends decides to uses himself to protect his "brother". He is immediately surrounded by energy and he fires it back at the surprised Tapir. The Tapir is shocked to see this much power pushing back his blast and is further horrified to learn that the King was using his life energy, which will kill him. He barely dodges the blast, just in time to see Gintoki, powered up by the King's energy, striking him down, the two men declaring that viruses can't defeat the Leukocyte King, Sakata GIntoki. In another area, the black and white body suited figures fight each other until an announcer on loudspeaker brings news of the Archfiend Tapir's defeat and the beginnings of restorations. The voice commands that the remaining 'viruses' should dress in white now and for both groups to reproduce.
Gintoki, along with the restored Kagura and Shinpachi, walk up to the dying Leukocyte King; the doppelgangers both admit that they broke their promises, the king to survive and Gintoki to protect the King. The King blames them for making him do uncharacteristic things, like sacrificing himself to protect them instead of just Tama and no longer wanting to die so he could have more fun with them. He believes himself to have become a faulty program that was still easily replaceable. Gintoki again responds that the King was no substitute and tells him not to die; he needs to live for his friends. The program starts to respond that they were better protectors than him until he was interrupted by Tama, who thanks the Yorozuya for protecting the program. The two teens find a tiny pixel Tama behind them and she explains that her systems weren't fully restored yet but she was able to send this mini her. She thanks her shocked security program for always protecting her and she decided to return the favor by entering the King's body to repair him; she will not let him die. Kagura suggests that the Yorozuya should help Tama but Shinpachi wonders how would they enter the King. The answer came from Gengai, who had shrunk himself to enter Tama slightly earlier, using the shrinking mallet on Shinpachi. Kagura panics and flees, being chased by the mechanic. Gintoki sits next to his stunned twin and tells him that his life was no longer his to throw away. He has become more than Tama's protector as this lead to others that will protect him in turn, like a leukocyte. The King gives a faint smile before stating again how much he and Gintoki were the same, since he couldn't bring himself to cry or say thanks. He asks Gintoki what would he do in this situation and Gintoki only answers, "Smile."
After credits, a group of leukocytes on a cliff sees a vast army of viruses heading their way. The haven't fully recovered from the Tapir invasion and they start to wonder how will they defeat the enemy with their smaller force. They are interrupted by the Leukocyte King, who commands them to not give up as there are others who suffer from similar struggles. Even if they are in a different place, they are still together under this strong banner of white. He charges ahead, followed by his men.