Gintama: Season 7, Episode 6

7 - 6: Arriving Late to a Reunion Makes it Hard to Enter

Gin is tricked into turning up to a reunion party with Katsura and Sakamoto. The two are unhappy with their lack of screen time and are determined to start a flashback arc, but they then get sidetracked trying to figure out the identity of a supposed fifth hero who supported them from the sidelines.