Gintoki, Katsura and Sakamoto finally start to remember about Kurokono but from this comes unpleasant memories that they rather have wanted to forget.
The true Joui War flashback starts with Gintoki sitting on the roof of an abandoned temple's outer gate as a sentry. Katsura appears behind him to ask about the enemies movements within the camp that was thousands of kilometers from their temporary location. Gintoki responds that they were heavily weakened due to their battle earlier and suggested that their group should attack. Katsura chastises his battle-hungry friend, stating that their side was also heavily weakened as well. He suggests that he should relieve his blood-lust with the equally battle-hungry Takasugi (who was on the ground near them). Gintoki tells him that they had a fight a month ago and haven't talk to each other since.
Sakamoto arrives on the roof, amused by Takasugi's and Gintoki's 'antagonistic' friendship and reveals the cause of their month-long feud. It turns out that during a down-time trip to a red-light district, both teens chose the same prostitute to spend the night with. The prostitute preferred Takasugi, but later tells Sakamoto that Takasugi spent the entire night being grumpy and glaring at her. The two angrily attack Sakamoto in retaliation then proceed to have a stare-down with each other. Oblivious about his role in angering the two teens, Sakamoto declares that they should go to another red-light district to calm everyone down. He and Katsura end up arguing with each other until someone (Kurokono) suggests that they should play kick the can.
As present GIntoki, Katsura, and Sakamoto wonder about the game, back in the past, Katsura reprimands Kurokono for the suggestion. The long haired teen is stunned to see Takasugi and Gintoki trash-talking each other as they quickly hide. Kurokono decides to play the demon and Sakamoto and Katsura hide in the surrounding bushes. As Kurokono counts down, Katsura notices that two bandaged men in their camp quietly opens the gate's doors. He realizes that they are spies and their enemies start to attack... an empty temple. Gintoki and Takasugi appear, revealing that they had set a trap for their enemies and had already evacuated their comrades, finishing off by Takasugi triggering bombs within the temple. The two and Katsura decide to retaliate, forgetting about both the game... and Kurokono, who was in the temple when it exploded.
In the present, the trio suspects that Kurokono died during that explosion and has become a wandering ghost, still playing kick the can. They are relieved at the revelation, except for Gintoki due to his fear of spirits. Katsura leaves to use the bathroom but comes across a can that a figure steps on. His scream is heard by Gintoki and Sakamoto, who decide to investigate while using the bathroom. Sakamoto leaves the bathroom, despite Gintoki's desperate pleas to stay, and also confronts the can and the ghost. Gintoki overhears the encounter and in a panic, rushes back to the room, singing the Doreamon theme song.
A camera watches his every move and it is revealed to be from Takechi and Matoko and a few Kiheitai in another room. The entire reunion party was a trap set by Tekechi to get rid of the remaining Joui 4 due to their threat level to their boss's plans, using the Kurokono name to lower the three men's guard. The unconscious Katsura and Sakamoto are tied up in the next room and with Gintoki on the verge of a breakdown, Tekechi decides to finish the silver haired man off by disguising himself and four other Kiheitai members as Kurokono (bandaged men dressed as bloodied basketball players). Tekechi fails to scare Gintoki but the other four corner him with their cans that spews sleeping gas and Gintoki falls unconscious.
In a dream/ flashback, Gintoki and a few other Joui soldiers are hiding in a forest, leaning against trees. Kurokono stops in front of a seemingly sleeping Gintoki, telling the teen that he is leaving the war. He is grateful for helping the group but has always felt inferior to the Joui 4, unable to do anything but fight in the shadows and not leaving much of a presence. Gintoki tells Kurokono that as long as one person remembers him, he'll be fine and to come help them again when they're in trouble. Kurokono thanks Gintoki and leaves adding that shadows are always by one's side. Gintoki snaps awake and kicks the sleeping gas cans back at the "ghosts", knocking them out. Gintoki apologies to the camera, stating that he finally remembers, that the real Kurokono, who didn't mind being forgotten, wouldn't stoop so low as to haunt someone. At the same time, the rest of the Kiheitai are knocked out with a figure pointing a sword at a stunned Matoko's neck. The figure, revealed to be the real Kurokono, tells her to release the hostages and leave the compound.
The next morning, Sakamoto and Katsura wake up, having forgotten much of what happened to them last night. Remembering the party, they rush to ask Gintoki about Kurokono. Gintoki, who had spent the rest of the night relaxing and reminiscing with the Fifth Man drinking Pokari, states he forgot.
After credits, Gintoki writes a letter to Sorachi (the mangaka of Gintama), telling him that they have animated the Patriot Reunion Party Arc but asks who was the figure always shown in flashbacks with the Joui 4 since he was not Kurokono.