Imagine Percy and Nico being soulmates, but Nico never put in the Lotus with Bianca. Nico grows up knowing something is missing and training to be the one of the prophecy. He eventually finds the Lotus hotel on a quest and ends up trapped, because he’s a loner. Percy goes on his first quest, but this time he has been warned of the Hotel because Chirion knows it attracts children of the big three now. (Due to Nico) When Percy encounters the hotel with Annabeth and Grover they still enter because they’re exhausted. Nico is now Percy’s age and when the two meet. Percy talks to Nico long enough for Nico to remember more of his past and the two escape with Annabeth and Grover. The four complete the quest without a hitch, Nico having the ability to calm his father and convince him to release Sally. The four then confront Ares and Nico gives Percy his pink triangle he received back in his own time when Annabeth gives her camp necklace and Grover gives the tin can. The four fly to return the lightning bolt, Percy and Nico comforting each other due to fear of air travel. They go to Olympus and things play out like in the books, with the exception of Zeus being “ugh. Hades’s brat is alive?!” Percy defends Nico and Poseidon is like, “You should probably go, Percy.” Then, Percy checks on his mom. They then go back to camp and all four are honored. Nico is astounded by the demigods and has a hard time processing everything, especially the slang. Chiron welcomes Nico back and the two share an emotional bonding moment that everyone is like, ‘daww’ at. Luke betrays Percy in the same way he did in the actual books. Then, at the end of the book, Percy asks if Nico can come live with him and Sally and Sally says yes. The two go to school together and its cute.
Second book plays out as normal, with the only exception being Nico sneaks out with Tyson, Annabeth, and Percy. (And Nico has to be comforted by Percy due to fear of water that’s similar to the fear of the air). Thalia is returned to a living state and the children of the big three kind-of clash, but not really because all three are there and Nico becomes a kind-of mediator.
Then, Bianca is released from the Lotus. Thalia, Nico, Percy, and Annabeth are sent when Grover IM’s about her. Nico recognizes her immediately and wants to run to his sister, but is held back by Percy, who tries his best to explain that she wouldn’t remember him. Nico knows this to be true but still hates it. Percy goes to rescue Bianca and Annabeth falls off the cliff. Artemis saves them and Apollo informs everyone of not only Thalia’s age, but Nico’s as well.
Nico, apparently, now has the same birthday as Percy and they are both the same age. The two find this cool and just high-five. Though Apollo is seen glaring at the back of the bus (where Eros sits invisible shooting an arrow in Nico). Nico idolizes Percy for a bit there because of how brave he was in defending his sister. Then, Nico starts to hate himself for feeling his feelings. (Remember the era he grew up in.)
Percy follows the hunters and grover on the quest, and promises Nico a similar promise as in the book, because, “While I can’t keep her safe or make her remember, you can at least keep her safe. Promise me, Percy!” When Percy returns and has to give the news of Bianca, it crushes Nico. And, were it not for the deep friendships he had already formed he would have likely run to Sally. Percy comforts Nico as best he can, and Chirion permits Nico to raise Bianca. Percy then gains the idea of contacting the Hunt and having them say their goodbyes to Zoe. Nico thinks this is a great idea and Chirion contacts Artemis.
They contact Bianca first, in-case she had anything to say to Zoe. Bianca remembers Nico,albeit faintly and the two share a “What might have been” moment before everyone else says goodbye to her. Then she leaves with a Thank you and telling Percy to not feel guilty (though everyone can tell he totally does)
Then they contact Zoe and a lot of the people cry. After everyone finishes (Annabeth ends up asking about the one-battle-i-can’t-remember-the-name-of for her dad, which Zoe finds sweet and gives percies details)
After the goodbyes are finished and Zoe is sent off Artemis thanks Nico and actually gives him a hug. (Whispering in his ear, “I know it hurts, but we both must move on.”) Everyone is stunned by this but most see it similar to when Thalia hugged Percy. (Platonic hugs are the best things ever.)
Then, Percy and Nico head back to Sally and finish off the school year.
The fourth Book is changed, simply due to Nico not running. So this gets a bit complicated to imagine. Let’s just say, Percy, Annabeth, Tyson, Grover, and Nico all go on the quest. Nico runs away after admitting his feelings and being scared of them. They run into him with Minos who is telling him lies. Percy convinces Nico to come with them. Rachel Elizabeth Dare is necessary. Pretty much the rest of the book is the same except Nico stays at camp at the end Percy ends up on Calypso’s Island she helps him figure out his feelings for Nico and during this she falls for him (he still grows a garden in New York to honor her) and Percico becomes a couple during the next school year because they both like eachother and Percy shows him different cultural things like, “Hey, It’s okay to be Gay."
Sword of Hades happens, and Nico comes back to Sally’s house after dealing with the Bob situation. Now, Nico and Percy have to deal with sharing the prophecy and Nico convinces Percy to bathe in the Styx. Sally gives approval. (And this time Percy isn’t captured by Hades because Nico would have memories of his mom (including Zeus killing her) and Hades understands they will share the prophecy.) Nico is what thethers Percy to the world.
Then Last Olympian pretty much plays out the same way, but Nico convinces his father, a bit easier, to help fight for Olympus.
Nico ends up with Percy and helps Luke make the decision. He then travels to the Underworld to garentee Luke to get whichever spot in the Undewrold he wanted.
At the celbration, Nico and Percy come out as couple to camp (cupcake scene and underwater kiss cannot be stolen from Percy)
Then Lost Hero happens and Nico reports back to Sally whenever he is not searching. He ends up in the underworld a few times and finds Hazel. He saves her and Hades guides him to be Pluto’s Ambassador.
During SoN, Percy remembers Nico. When he sees Nico he demands information and Nico tells him honestly and Percy can see the pain and sincerity in Nico’s eys "I wish I could tell you, but I can’t. You need to find out on your own, no matter how much this hurts I’m sorry.” Percy doesn’t like it, but accepts it after Nico begins to have tears stream down his face.
When Percy regains his memories in SoN, he gets frustrated at Nico but understands and cares about him a ton.
Annabeth is still the one of the seven and she was still worried. (Hey, you have that close of a friendship with someone, wouldn’t you judo flip them for being gone that long?) The seven end up sailing and MoA happens. (Only there is a kiss when Nico and Percy are reunited.) Percy still cares about Annabeth and still ends up helping her (because, again their best friends. Come on. Platonic love exists people!) So, then Percy and Annabeth still fall into Tatarus. Nico and Percy shout 'I love you’s as Percy falls, both sobbing and Annabeth shocked Percy would fall with her.
Nico leads them to the House of Hades (Cupid sequence is Nico admitting he still feels like he shouldn’t like guys in that way and cupid being a freaking nice character and actually helping Nico with his feelings, and Jason being a good person and accepting Nico and becoming his friend though discussion and shared experience.)
House of Hades then on happens similar to how it did in the book, but with platonic-still-deeply-care-about-eachother-just-not-romantically-okay-Percabeth instead of romantic-lets-kiss-type Percabeth. When Nico learns about Bob he freaks out and just Nico-sadness.
Then, Nico volunteers to Shadow Travel with Reyna and Coach to get the Athena Pathenos to camp. Percy doesn’t want him to leave, but Nico promises to see him soon. (Kiss moment) Then the three leave and the seven are off to Athens.
Blood of Olympus happens (but with more actual blood.) Annabeth and Percy get seriously injured (though they don’t die) and when Apollo gets there he can partially heal them, but they cannot fight geia directly due to the sheer amount of injuries. (Plus he’s like “Woah! You two need to talk to me later because I need to physco analyze you. Tatarus did some serious crap to you two. And Nico went there too? Gosh dammit, take him along to. when you meet with me, okay?”) (So, there, reason for no direct fighting) When the giants were fighting frank, the one with control over fire almost burned his stick to a crisp, so he decides to sit out the direct battle, due to the “Storm or FIRE” part of the prophecy. Everyone is pretty much okay with this because, “WE CAN’t LET YOU DIE FRANK” Hazel, however, climbs on Festus and helps destroy Mother Earth. She uses the soil in the airborne body of Gaia to morph the earth goddess and make her more vulnerable. Piper works on Lulling her back to sleep with a lullaby so strong most wear earplugs. (Plus, Leo helped by giving her megaphone) Leo works on his fire part. Nico is still fading from shadow travel, but he, along with Percy, Annabeth, Tyson, Grover, Frank, and Reyna convince the two camps to stop fighting, though there have already been many casualties. (Most well known being Clarisse, having died protecting one of the younger campers (whom she had earlier been teasing) who had snuck up to help fight. Octavian fires himself, though many try to stop him. Jason flies Hazel and Piper to the ground in time and Leo promises to jump and says him “you’ll have to catch me” line from Lost Hero. Leo doesn’t jump and with the combined efforts of Hazel, Jason, Piper, Festus, and the two sacrifices of Octavian and Leo Geia is defeated.
Leo saves Calypso from Oygia and the two return to camp to find his memorial being presented by Nico with the 7 and coach hedge speaking on his behalf. The two wait until Coach finishes to enter the area. Annabeth just cries out, “NOT AGAIN” (Because of Percy and MT. St helens) and Nico chuckles. Piper punches Leo in the face after he makes a joke and the 7 + Nico and Coach hedge give him hugs. Calypso and Percy fist bump and Percy apologizes for not following up with the gods.
Then, Celebration is had for Leo’s return and Nico and Percy make sure the two get dumped in the lake for their initiation.
