A Little Spoiler - don't know if it's confirmed or not.
- The fire Festival is actualy a party where someone marries - and so it happens that Orochi and Zoro are marrying at the fire Festival on onigashima.
- But Zoro didn't tell anyone yet
- And appearantly there is also a Little plot Twist - it seems that Zoro also loves Killer and wants to marry him aswell.
I don't think it's confirmed yet, but seems legit.
Source: onlytruespoiler.net