Okanoah

Okanoah was the first canon ANGST UNIVERSE relationship.
It is between Okami Demesu and Noah Yuna, both male side characters who had a pretty big arc.

History:
Noah met Okami one day and let him and his sister Akari Demesu(tho she isn't relevent anymore). Evetually the two started dating, murdered each other's homophobic parents and got married.

Episode appearances:
The entire Demesu-Yuna arc.
Backstories of some.
The beach episode!