Gintoki came to a reunion party of the Joui patriots, for which he was late. Katsura and Sakamoto mocked him for his lateness and jokingly talked about how he always acted on his own and left the two to clean up. As a result, an annoyed Gintoki wanted to leave, but was kept back.
Katsura then suggested having an arc about their past in celebration of Gintama's 10th year anniversary. Gintoki was against the idea, saying that the most boring people in a class reunion were the ones who talked loudly about the past. While so, Katsura believed that it was that kind of thoughts that led the series to nowhere after 10 years.
He pulled out a letter - an invitation to the party from another member of the Joui patriots. Though, Gintoki (and later Sakamoto) did not seem to remember who he was at all. According to Katsura, he had supported them from behind, and his name was Kurokono Tasuke. The group then tried to recall their memory about Kurokono before he came, thinking that it would be embarrassing if they were found no remembering him at all.
Katsura was the first to recall a memory, which was set in a basketball match instead of the Joui War, (much to Gintoki's frustation.) In this memory, due to his long hair, Katsura could only cheer his comrades from the sidelines with his dry throat and a frozen bottle of Pocari. Then, it was Kurokono Tasuke who warmed the Pocari bottle for him.
Sakamoto got on the line with Katsura, recalling another memory. In this one, he ran out of toilet paper in the toilet and was assisted with a bottle of Pocari as a replacement. Got out of there, he met another comrade, who was, in fact, Katsura from the basketball match. Katsura added that it was him who gave Sakamoto the Pocari bottle.
Gintoki, angry, asked where Kurokono was and why the others kept talking about Pocari. Katsura reminded Gintoki of a battle during the war, after which the two survived, completely thristy. Then, they ran into a vending machine that sold Pocari. They discussed about splitting their money and got back to the formation, where all four Joui patriots argued on the amount of money Gintoki owed them. At present, Katsura and Sakamoto asked Gintoki to give their money back.
Just when Gintoki, having lost his patience, was about to leave, they were informed that another guest had come to their party.
The name "Kurokono Tasuke" and the setting of Katsura's memory is taken from the manga series Kuroko no Basuke.