ChiHaya

ChiHaya is the het ship between Ryūnosuke Chiba and Rinka Hayami from the Assassination Classroom fandom.

Canon
Chiba and Hayami have a steady friendship and are proven to have romantic feelings for one another, although whether they're actually "together" is unknown. The two have gone on dates but they always ended awkwardly since neither could hold up a conversation for very long.

Chiba is the best shooter in the class, with Hayami close second, the two were paired together with the task of shooting Korosensei while he was pinned down by the other students. They were paired together again in Korosensei's Assassination Test of Courage.

In the guidebook, it's said that they both talk more if they're talking to one another, likely because they feel that the other understands them better than other people. The two are known in the class as the gunmen and for being calm and quiet.

After guadation, Hayami helped Chiba set up his own architect business and the two are still friends.

Fanon
They are a decently popular pairing among the fandom.

Hayami and Chiba are the only ones who understand each other and confide in each other whenever feeling stressed, when normally they would just hide those emotions.

Fandom
FAN FICTION 

Trivia

 * Chiba's favorite food is hard-boiled eggs and Hayami's is beef stroganoff.
 * Hayami and Chiba scored their first kill together in Civil War by sniping Takebayashi.