So Yuuri and Yuuko always give each other both a normal gift and a gag gift for holidays, celebrations, etc. And when Yuuko's wedding comes around Yuuri's gag gift to her was a step by step tutorial of pole dancing with a slow-mo video of him pole dancing with stripper music in the back ground at the end. Yuuko lost her shit and keeps it in a precious box for years. But then she brings it to the Viktuuri wedding. Everyone is now asking for copies and Yuuri realizes he's friend with a traitor.
OH MY GOD