Often referred to as "the golden pair" both in the anime/manga and as a nickname for their pairing, the Eiji/Oishi pairing is from The Prince of Tennis.
The two are a doubles pair who are able to synchronise together as all great double pairs can. Because of their close relationship as partners in tennis and great friends this is an easy pairing to make - the two are already close so going a little further is not beyond imagination.
Oishi is the vice-captain for much of the program, and while both players are capable of singles, they both prefer to play as doubles, especially together.