Elysion

Elysion by Rayless Night is a Persona fanfic dealing with the popular idea of crossing over Persona 3 and Persona 4.

Life has moved on past a more or less "happily ever after" ending for the heroes of Persona 4, but not for the remaining heroes in Persona 3. Someone is targeting Persona users, and Detective Naoto Shirogane is on the job. Kidnapping, torture, and murder abound, and someone who we all thought was good turns out to be manipulating events and taking lives in order to save the soul of one boy, even willfully giving up her soul in the process. The plot is darker than the stories of both Persona 3 and (especially) Persona 4, given the betrayal and sacrifice at a level not seen in either game, but is arguably one of the most popular Persona 3/4 fanfics.

Tropes used in Elysion include:

The Ace: Souji tends to be this.
Anyone Can Die: Ken, Koromaru, Aigis, and Mitsuru die over the course of the story. Though Ken and Koromaru were already dead by the time the story started.
Bittersweet Ending
Badass: Souji retains this from the game. For crying out loud, he, along with Yosuke, infiltrates a heavily guarded compound armed with only a golf club, and without being able to use his persona.
Badass Crew: The Investigation Team.
Big Bad: Mitsuru. Subverted. She's working for Kronos.
Character Focus: Naoto, Kanji, and Akihiko get the most focus.
Darker and Edgier: Especially so for the heroes of Persona 4, but even so for the already-traumatized crew from Persona 3.
The Dragon: Kampe, an antishadow weapon, to Mitsuru. Mitsuru, to Kronos.
Face Heel Turn: Mitsuru.
The Generic Guy: Souji falls into this. Lampshaded by Naoto's grandfather.
- Standardized Leader:
  - The narration of the story tends to focus on the other characters rather than him.
  - Souji's presence is one of the big differences between the Investigation Team and SEES.
Jigsaw Puzzle Plot
Love Hurts
Necromantic: Mitsuru's original reason for allying with Kronos.
Redemption Equals Death: Mitsuru
Storming the Castle: Akihiko, Junpei, and Aigis break into the Kirijo Estate at the same time as the Investigation team.
- Bonus points to Souji and Yosuke for storming said castle armed with only two knives and a golf club while everyone else already had their Personas by that point.