Perfect Number is a South Korean mystery drama film directed by Bang Eun-jin and starring Ryu Seung-bum, Lee Yo-won, and Cho Jin-woong. The film is a faithful yet free adaptation of the third part of the series by the popular Japanese novelist Keigo Higashino, called "The Devotion of Suspect X."
The story follows the life of Suk-go (Ryu Seung-bum), a brilliant but socially awkward mathematician who lives in an apartment in Seoul. One day, he comes to the aid of his neighbor, Hwa-sun (Lee Yo-won), after she accidentally kills her abusive ex-husband in self-defense. Suk-go becomes drawn into Hwa-sun's life and decides to help her cover up the crime by creating a perfect alibi.
However, Detective Cho (Cho Jin-woong) becomes suspicious of the alibi, and he starts to investigate the case. As Suk-go and Hwa-sun's alibi starts to crumble under Cho's scrutiny, the mathematician realizes that he must use his genius to save Hwa-sun from a life behind bars.
The film's plot is intricate and full of twists and turns, keeping the audience engaged until the end. The performances of the lead actors are superb, with Ryu Seung-bum delivering an excellent portrayal of a man consumed by his love for Hwa-sun.
Overall, Perfect Number is a gripping and intelligent thriller that explores the themes of love, obsession, and murder, making it a must-watch for fans of the genre.