At the start of the game, Hagakure tells Leon to cheer up since he believes the situation they're in is the school's orientation procedure, which calms him down. Later during Chapter 1, Leon uses and breaks Hagakure's crystal ball as a way to get rid of evidence, which obviously upsets him.
In Danganronpa IF, the two are usually arguing, first over Hagakure's late reaction to Makoto getting impaled, and when Leon breaks his crystal ball, again.
Both are the main Danganronpa 1 characters of the novel "Ultra Despair Hagakure", although they don't interact because Leon is already dead during the events of the novel and only appears in Kanon Nakajima's flashbacks.
The ship sailed as a result of the two usually being considered two of the least interesting Danganronpa 1 characters due to how little character development they get to have initially. However, this was helped with the novel titled "Ultra Despair Hagakure". In some cases, the ship may result from a Pair the Spares scenario.