Glances at each other across the room.
Secret smirks in meetings.
You could say they were making history.
I mean, who else in the history of suspect and investigator were involved like they were? Sexually, romantically, they never really put a label on it. All they knew, was when the rest of the Task Force went home, they were kissing and taking off clothes and falling over furniture on the way to the shared bedroom.
Of course, the next day, they acted no differently around each other. No one would suspect a thing unless you could read their minds. Then, you could hear Light's comments about L's appearance or you could listen in as L inconspicuously analyzed Light from that perspective.
Then, you would know.
L might be making history as the world's greatest detective.
And Light might be making history as the supposed God of the New World.
It didn't really matter. They were already making history on each other.