Warning! This article contains spoilers for The Hidden Oracle.
- “I apologize for my boyfriend.'
'Could you not–'
'Would you prefer special guy? Or significant other?
'Significant annoyance, in your case.”
- —Will and Nico, in The Hidden Oracle.
The Blood of Olympus
When Nico arrives at the camp near Thalia's tree, he is surprised to see Will planning on stalling the Romans. Will tells Nico he is doing this to get fresh air after helping Mellie give birth to her baby. Holding Nico's hand, Will shows how nervous he is from helping her give birth. This action "sent an electric current" down Nico's spine, so he withdraws his hand in shock. Will immediately notices Nico's condition and nags Nico on not using shadow traveling anymore, since it is damaging his health. The two continue to bicker throughout their mission: making sure the Roman onagers would not fire on Camp Half-Blood.
When Nico states that he is leaving both Camp Jupiter and Camp Half-Blood, Will becomes upset and demands a reason, berating him for thinking he doesn't belong. Will reassures Nico that he has a lot of friends at camp, and there are many who want to be his friend.
Later on, Will asks for Nico's company in the infirmary. When Nico confesses his feelings to Percy (these feelings would later fade due to Nico losing interest and Percy's relationship with Annabeth), he walks away toward Will. This can be seen as symbolic of Nico ultimately choosing Will over Percy in the end. After meeting Will outside the camp, Nico remembers when Will first arrived with Apollo at the camp years before. At that time, Thalia had referred to him as hot. Nico doesn't understand why he is suddenly thinking of that moment, but it is likely an indication of his attraction to Will. Nico thinks of the moment when he first met Apollo, Will's father, and how Thalia had called him "hot," too. He ponders the similarities between Apollo and his children.
The Hidden Oracle
At some point during the ensuing months, Nico finally comes out and confesses to Will Solace about having a strong crush on the latter, and the two begin dating. In order to sit together with his new boyfriend during meals, Nico claims to Chiron that he somewhat loses control of his infernal powers while sitting alone. Therefore, Nico is given permission to sit at the Apollo's Cabin's table instead, as Will produces a handy fake doctor's note, and Chiron decides it isn't worth arguing about.
Solangelo was largely popular after the events of The Blood of Olympus. Will and Nico's interaction remained minimal throughout the events of the series before the final book. After the slight implications of Nico possibly liking Will and Riordan confirming that Nico is queer, Solangelo has been getting more attention. Although, some fans still cling to Percico over Solangelo. Many Solangelo fanfictions includes fics about what happened in the three days of rest of the infirmary.
After Rick's confirmation about Solangelo on his Twitter, fans were excited and overjoyed and Solangelo has been confirmed as canon and has been getting more and more attention since the release of The Hidden Oracle.