[3] Yagami manages to see the connection between the suspect Akihiro Ehara and his links with a series of murders committed against bullies in Kamurochō and Isezaki Ijincho.

In Lost Judgment, the player controls Takayuki Yagami as he explores the Japanese cities of Kamurochō and Isezaki Ijincho (recreations of the real-life Kabukichō and Isezakichō districts, respectively).

[6] New to Lost Judgment is the "Detective Dog", a Shiba Inu named Ranpo whom Yagami can take on walks to find hidden items or track suspects via their scent.

Private investigator Takayuki Yagami (Takuya Kimura/Greg Chun) returns as the primary protagonist, alongside several of his supporting cast: Masaharu Kaito (Shinshū Fuji/Crispin Freeman), Ryuzo Genda (Akira Nakao/Brian McNamara), Saori Shirosaki (Yūko Kaida/Stephanie Sheh), Issei Hoshino (Yū Hayashi/Joe Zieja), Mafuyu Fujii (Risa Shimizu/Cherami Leigh), Toru Higashi (Yoshihisa Kawahara/Steve Blum), Fumiya Sugiura (Junta Terashima/Mark Whitten), and Makoto Tsukumo (Jun Miyamoto/River Kanoff).

The central figure of his investigation is Akihiro Ehara (Ken Mitsuishi/Artt Butler), a Tokyo Metropolitan Police Department Officer accused and held in custody for groping, while also linked to the murder of Hiro Mikoshiba (Shohei Kajikawa/Andrew Morgado), a student teacher at Seiryo High School.

Aiding Yagami in his investigation is Jin Kuwana (Koji Yamamoto/Todd Haberkorn), a mysterious handyman with ties to the incident; Tesso (Jun Kasama/SungWon Cho), the leader of the Yokohama Liumang gang's White Mask branch; and Kisuke Watanabe (Shigeo Kiyama/Edward Bosco), a detective working for the Kanagawa Prefectural Police.

As part of his investigation at Seiryo High School, Yagami also becomes acquainted with Mami Koda (Misuzu Togashi/Kayli Mills), a student who is targeted by several bullies in her class, and Yoko Sawa (Mai Yamane/Erica Lindbeck), an English teacher who oversees Koda's class and is connected to Ehara's son, Toshiro, who committed suicide several years ago.

Other characters featured in the main story include: Yuzo Okuda (Yusaku Yara/Jamieson Price), the chairman of Seiryo High School; Reiko Kusumoto (Marika Hayashi/Sumalee Montano), the Vice Minister of Health who took the position following the arrest of her predecessor, Kaoru Ichinose; and Hidemi Bando (Yutaka Aoyama/Andrew Kishino), an officer of the National Police Agency's Public Security Division.

The Kaito Files expansion stars Kaito as the primary protagonist, and features a brand new cast of characters, including: Kyoya Sadamoto (Katsuyuki Konishi/Stephen Fu), a highly successful tech CEO; Mikiko Sadamoto (Eri Miyajima/Suzie Yeung), Kyoya's wife and Kaito's former lover who was thought to have committed suicide; Jun Sadamoto (Yuki Shin/Paul Castro Jr.), Kyoya and Mikiko's rebellious teenage son; Shusuke Kenmochi (Hiroshi Nakamura/Alexander Gross), leader of the Crimson Lotus gang; Masao Igarashi (Taichi Takeda/Peter Jessop) and Shiro Senda (Tōru Nara/Dave B. Mitchell), former yakuza members who now run the Bato Detective Agency as a rival to Yagami's business; and Yasutaka Shirakaba (Kenta Sasa/Yong Yea), a doctor residing in the Chiba Prefecture who has ties to Mikiko's disappearance.

Shirosaki explains that one of her defendants, Akihiro Ehara, who is held in custody for sexual battery, told the court about the whereabouts of Hiro Mikoshiba's body in Ijincho before the police could find it.

Okuda overhears and reveals his motives for requesting the detectives; he seeks to disprove Ehara's accusations that Seiryo High is negligent in terms of bullying.

Yagami discovers that the RK invasion was led by Hidemi Bando, coordinator of the National Police Agency's Public Security Division so that he could engage in a smear campaign against Reiko Kusumoto, Mitsuru's mother, who is also the Vice Minister of Health.

Bando sought to remove Reiko as the supervisor of the national pension fund since he planned to gamble it to revive Japan's stagnant economy.

To resolve this, he decided to expose her secret of murdering Shinya Kawai, one of Mitsuru's bullies; he intended to capture Kuwana and his students so that he could make them testify against her.

Sadamoto asks Kaito to find his wife Mikiko, who allegedly committed suicide two years prior but was recently spotted in Kamurochō.

Traveling to his home in Chiba, they meet Yasutaka Shirakaba, a doctor who admits to faking Mikiko's death to protect her from a gang that was looking for her.

He claimed "About a year ago when we were in the initial phase of development there was no lockdown in Japan, and the situation wasn’t as severe, but once we entered the final stages of production, things were getting serious and it became harder to communicate.

As a result, the characters feel more realistic, with the tailing targets now breaking out into jogs, turning back when they hear sounds, and he hopes that players notice this.

The plot was written to be realistic, something the staff found challenging while providing themes seen as sensitive to the audience like bullying as well as what should people call justice, with the latter being explored through Yagami's characterization.

[26] Hosokawa said the team read books from authors like Keigo Higashino and Hideo Yokoyama when preparing to write the game with the former's novel The Devotion of Suspect X being a major influence.

Strichart commented that Yagami is not a hero so he is not able to solve all these cases on his which contrast the fantasy style Persona 5 which often deals with the protagonists saving victims using their powers.

As a result, he claimed that for the sequel "the game kind of teed me up to really be in that Yagami mindset where, yeah, I love being a detective, but some cases are real bummer and super boring."

[33] Aside from Chun reprising his role as Yagami, returning cast members include Crispin Freeman as Masaharu Kaito, Brain McNamara as Ryuzo Genda, Mark Whitten as Fumiya Sugiura, River Vitae as Makoto Tsukumo, Joe Zieja as Issei Hoshino, Steve Blum as Toru Higashi, and Cherami Leigh as Mafuyu Fujii.

New English cast members include Artt Butler as Akihiro Ehara, Brent Mukai as Daimu Akutsu, Todd Haberkorn as Jin Kuwana, Erica Lindbeck as Yoko Sawa, Kayli Mills as Mami Koda, Xanthe Huynh as Kyoko Amasawa, Edward Bosco as Kisuke Watanabe, and Aleks Le as Shinya Kawai.

Returning actors such as Matthew Yang King, Jamieson Price, Yuri Lowenthal, SungWon Cho, and Keith Silverstein voice new characters entirely, being Kazuki Soma, Yuzo Okuda, Sadao Takano, Tesso, and the Owner of Bar Siren respectively.

[34] Following the release of the game, Sega staff felt that if there should be a sequel to Judgment, Yagami and his partner Masaharu Kaito would retain their lead roles and would still be set in Kamurocho.

The reviewer further praised the handling of the narrative as it focuses properly on several conflicting themes, like issues with the law, bullying and sexual harassment.

[61] Shacknews enjoyed the improved visuals but felt the main plot was a "mess" due to how difficult is to understand, with Ehara's case being focussed on for several chapters, which makes the pacing poorly handled.

[66] Eurogamer outlined in their review that "RGG Studio's broadest, most packed open world is matched by mediocre additions and an ill-fitting story.

[82] While the gameplay was found to be enjoyable for giving the player different fighting styles from Yagami's in the main game, it was still criticized for being noticeably smaller despite the price.