Nico always knew that Will liked him. But, he kind of wanted to see how long it would take him to make a move. Unfortunately, when 3 months passed with Nico knowing the truth and Will still didn't do anything, he decided it was time to do it. Nico never went for I like you and all that stuff. Literally, all he did was grab Will one day, kiss him and that was it. And Will was just like "HOW DID YOU KNOW? WHO TOLD YOU? WAS IT DREW? I SWEAR TO GODS I TOLD HER NOT TO TELL YOU! HOLY APOLLO WHY?"

When they started dating, Nico kind of... forgot... to tell his friends. Hazel was the only one who knew because Nico told her right after it happened. But the others... He totally forgot.

So when Piper walked in the Hades Cabin and saw them cuddle, her eyes widened and she yelled "WHAT THE HECK NICO!

And all Nico said was, 'Ah, yes, we're dating. I forgot to tell you. Oops.'

'OOPS?'