'100 Days of Deception' writer reveals why Kim Yoo Jung and Park Jinyoung were perfect for their roles

The writer of tvN’s upcoming drama 100 Days of Deception has shared why she was confident in casting Kim Yoo Jung and Park Jinyoung as the story’s two leads.

Ahead of the drama’s October premiere, writer Ryu Bo Ri opened up about working with the cast and director Yoo In Sik, while explaining what made Kim Yoo Jung and Park Jinyoung stand out for their characters.

100 Days of Deception is a period spy romance set during the Japanese colonial era. The story follows Gyeongseong’s skilled pickpocket Ga Gyeong, played by Kim Yoo Jung, who becomes a spy, and elite interpreter Tae Woong, played by Park Jinyoung, as their paths cross inside the Japanese Government-General of Korea.

For Kim Yoo Jung’s role, Ryu Bo Ri said the character needed an actress who could convincingly deceive both the people around her and the audience.

“Because Ga Gyeong’s acting ability and talent for lying are important parts of the story, we absolutely needed an actress who could captivate both the characters in the drama and the viewers,” she explained.

The writer said the role also required someone capable of handling Japanese and English while portraying major emotional changes throughout the story.

According to Ryu Bo Ri, Kim Yoo Jung immediately felt like the right choice.

“We needed an actress with the dedication to speak Japanese and English skillfully and the explosive power to convincingly portray a character who goes through major changes. The answer was Kim Yoo Jung,” she said.

Ryu Bo Ri was equally enthusiastic about Park Jinyoung, praising both his detailed acting and his reputation for being dedicated on set.

The writer revealed that she had followed Park Jinyoung’s acting career since his early days and was impressed by what he brought to Tae Woong.

“Even though I had watched and supported almost every project he has done since the beginning of his acting career, I cannot count how many times Park Jinyoung’s eyes, expressions, and voice as Tae Woong made my heart race or brought tears to my eyes,” she shared.

She added, “If the word ‘sincerity’ could take the form of a person, I think it would be Park Jinyoung.”

Ryu Bo Ri also praised director Yoo In Sik, known for works including Dr. Romantic and Extraordinary Attorney Woo. She jokingly said working with him made her wonder whether she had “been an independence activist in a past life,” describing the opportunity as feeling like she had gained a powerful ally.

The writer explained that the drama began with questions about the sacrifices made by independence activists and eventually developed around the idea of love — particularly the desire to create a better future for people one cares about.

She also highlighted the drama’s fictional premise of an independence movement sending its own spy into the Japanese colonial administration, along with the importance of interpreters who can control how information moves between people speaking different languages.

Kim Hyun Joo, Lee Moo Saeng, and Jin Sun Kyu are also among the cast members, with Ryu Bo Ri praising their performances and preparation for their respective roles.

100 Days of Deception is scheduled to premiere on tvN on October 10 at 9:10 p.m. KST.