Dear Old Dad is a Persona 5 Alternate Universe One-Shot Fic with a simple premise: all the Phantom Thieves of Hearts (minus Joker/Akira Kurusu and Morgana) are abandoned children of Masayoshi Shido, just like Goro Akechi.
Except Akechi only learns this right before the confrontation in Shido's Palace. Hilarity Ensues.
Dear Old Dad provides examples of:
- Adaptational Villainy:
- As vile as Shido was in canon, he was never shown to have attempted rape or sexual assault beyond the incident that got the Protagonist put on probation. Here he's an out-and-out Serial Rapist.
- Yusuke and Haru were conceived as a result of Ichiryusai Madarame and Kunikazu Okumura, respectively, pimping their mothers out to Shido. Haru, in particular, is so disgusted by her "father's" actions that she completely forgives Akechi for killing him.
- Abusive Parents: In addition to his canonical horrific treatment of Akechi, Shido is also Ryuji's abusive Disappeared Dad, drove his daughter Futaba into becoming a suicidally-depressed Hikikomori to cover his own ass, and has planned to (and tried to) kill all his bastard children. And Ryuji.
- Beyond Redemption: Shido is given this view by every Phantom Thief, and will be killed by them as a result.
- Big, Screwed-Up Family: Zigzagged - the Phantom Thieves have issues, but are all unambiguously decent people. Akechi and Shido are both parts of said family, however, and the latter in particular provides all of the "screwed up" part that is needed.
- Black Comedy: Shido having Akechi as his bastard son who resents him due to his mother's suicide and his Parental Abandonment? Horrible. Every last member of the Phantom Thieves but Joker and Morgana (and legitimate but abandoned son Ryuji) being his bastard children? Darkly amusing.
- Chivalrous Pervert: Ryuji describes Akira as this. Given that he apparently slept with every single one of Shido's children, he has a point.
- Child by Rape: Every Phantom Thief except Joker, Morgana, and Ryuji (and maybe Akechi) was sired by Shido under circumstances of questionable or outright non-consent.
- Cooldown Hug: Metaphorically at first, discovering that he has six half-siblings he never knew about shocked Akechi out of his initial fury. Then, Ryuji gives him a normal Cooldown Hug when he's told that Ryuji is Shido's "legitimate" son.
- Corpsing: When Akechi tells the Thieves that he's (also) Shido's son, Joker is left struggling not to laugh.
- Death by Adaptation: It's not done onscreen, but the Phantom Thieves, after discovering that Shido is the mutual father to most of them, have resolved to just kill Shido rather than change his heart. Makoto even flat out admits that they know it's murder, they just don't care.
- Good Stepmother: Or more specifically stepfather in the cases of characters with canonical fathers replaced by Shido, such as Ann and Makoto. This does not include Haru.
- Heroic Bastard: Shido's children are all infinitely better people than him, including Akechi, and he makes a HeelFace Turn.
- It's Personal:
- The Phantom Thieves are in the stages of Tranquil Fury, but at this point, all of them except Morgana has a very personal reason to hate Shido. And Morgana probably hates him on general principle.
- Futaba understandably hates Akechi for being the reason behind her mother's death and is very openly in favor of killing him.
- Laser-Guided Karma: All of Shido's bastard children team up to take him down.
- Luke, I Am Your Father: Everyone (aside from Joker and, obviously, Morgana), but of all people Ryuji turns out to be Shido's only legitimate child.
- Make an Example of Them: The circumstances that led to Makoto's conception; Shido arranged for her mother to be abducted and brought to him as a warning to her father, who was investigating some Yakuza he was connected with. It didn't work.
- My God, What Have I Done?: Akechi seems to be genuinely horrified when he realizes his murder of Wakaba Isshiki inflicted the exact same circumstances of his awful upbringing upon Futaba.
- Not So Different: Ryuji admits that he initially was a "Well Done, Son!" Guy to Shido as well like Akechi is, and he uses this to help him move past it.
- Related in the Adaptation: The fanfic makes Shido the father of most Phantom Thieves.
- Serial Rapist: Shido, simply by virtue of having explicitly raped or sexually extorted at least six different women. See Child by Rape above.
- Sexual Extortion: Shido forced Futaba's mother Wakaba Isshiki to sleep with him under threat of sabotaging her research, or making her leave the cognitive psience division of research.
- Spared by the Adaptation: Akechi survives as the Thieves plan for him to Take The Heat after killing Shido.
- You're Not My Father: None of Shido's children refer to him as "dad" or "father" in a non-formal sense, even Ryuji. They just call him Shido. Also in Haru's case, she gives Kunikazu Okumura the same treatment.