"Sing loudly, Divine Comedy!"
They are from the same world...
"Sing it, the magic song!"
They have opposing Zanpakutō...
"Long time no see~"
They have been best friends since childhood...
"Yo! You have become a eldest lady!"
They are he and she respectively...
"Why? Because we are friends! Best buddies!"
However, they are not lovers, they are friends, very good friends.