Post canon where Near recruits Sayu, Linda, and several other OCs maybe in a sort of elite Detective team, where my martial arts prodigy!Sayu applies. Think Leverage but a government sanctioned investigative team who also does arrests. I'm thinking if there's something better I can equate with that.
They're mostly dealing with organized crime. We get side dishes of Near and Linda's memory of Mello and Matt, Linda being Near's confidant and knowing about the first Kira. Sayu having grown up having occasional interest in martial arts as well as several other extracurricular activities but never committing until during her recovery- the belated guilt of if she'd just strong enough then maybe-. Near being taken off guard by Sachiko relating with him and the grief of having lost so much in the Kira case (after being introduced as someone who'd worked with her husband and son by her daughter).
The story starts with Near visiting the father and son Yagami graves, not for the guys but for the young woman visiting. They have a short interaction where Near introduces himself as someone who worked with her brother, and Sayu asking what he was like from his perspective, and Near eventually replying "Brilliant. He was brilliant." Idk. Then he walks away back to his limo and to the base, where Linda is already reviewing cases and complaining about essentially being forced into the team, they have a sister-brother relationship if the sister was a loose Cannon that had left him for her hobbies as soon as possible and the brother was an emotionally blank person. Near reviewing some files suddenly says someone evil can also be brilliant.
Matsuda is Sayu's pseudo big brother except they never say it bcs of issues, where he'd really stepped up for the mother-daughter duo during the worse time of their lives and now Sachiko fusses over him and sends him off with packed food and he drives Sayu to visit her father and brothers graves for the first time after physically recovering and being able to walk up the hill on her own. He's become rather dependable in the office, proud of the first martial arts competition she won, fusses over Sayu deciding to be a police and entering the academy, and worries even more when she joins a special training program who's details she cannot disclose but mostly lets her be and only ever drinks himself to sleep the night after Light's death anniversary that no one outside the Task Force knows. Eventually, after the squad is already going steady for a couple of months now, Matsuda finds himself sitting across a familiar boy-now-man and realizing exactly what Sayu had gotten into and being very quietly but not secretly unhappy about it as he glares at Near, and seethes at the memories and wonders how Matsuda himself looks in those silently considering eyes watching Matsuda enjoy the family of a man he killed.
Near is the mastermind, Linda the right-hand grifter/undercover 'more social person to talk to when the leader of the group is being too infuriating', Sayu does the footwork and is the muscle, we have an OC driver, and an OC hacker and whatever else you want. Different nationalities. This is more crime/mafia genre than canon, but the slightest touch of supernatural as we stumble into impossible-to-solve cases one after another that they have to solve..
Now this part is optional, but also non-toxic whirlwind romance-before-tragedy SayuxMello is my guilty pleasure so we have Sayu wearing a rosary and Near occasionally staring at it, the memory of Mello sitting between them except Sayu doesn't know and Near will never bring it up but it does complicate things when he possibly catches feelings. The rosary may also possibly be a key element in one of their biggest cases as it turns out to be a USB Mello had entrusted to Sayu, as sort of a promise token that 'I'll come back if I'm not dead' and Sayu knows is a USB, but also knowing where and how she met Mello, never dared to hook it up.