Reigisa

Reigisa is the Slash ship between Nagisa Hazuki and Rei Ryugazaki from the anime Free! Iwatobi Swim Club/Eternal Summer series.

Canon
Nagisa and Rei first met when Nagisa was trying to recruit members for the swim club. He saw Rei's pole vault and thought that his dive was perfect. Nagisa then started insisting that he join the team.

Fanon
AO3

Trivia

 * Nagisa's animal symbol is a penguin, while Rei's is a butterfly
 * In the abridged series, 50% Off, the two are an official couple
 * One of Nagisa's resons for Rei to join the swim team is that Rei has a name that is traditionally for a girl, just like the other three members, and Rin.