Byun Yo-han, left, plays the role of Jeong-tae in the new thriller film "Following." Courtesy of Content ZIO

There's nothing funny about murder and stalking. But the upcoming thriller film "Following" manages to put a touch of humor in its suspenseful mystery story.

Director Kim Se-hwi / Courtesy of Content ZIO

"Our movie has a very fast-paced and captivating story, along with a lot of humor," the film's director Kim Se-hwi told The Korea Times during an interview at a cafe in Jongno District, Seoul, Wednesday.

The mystery thriller, set for release on May 15, follows realtor Jeong-tae (Byun Yo-han) who has a perverted hobby. He enjoys peeping into other people's lives, sneaking into their homes using the keys his clients left for him.

One day, a social media influencer, So-ra (Shin Hye-sun), catches his interest after seeing her posting a vegan salad as her meal on Instagram while eating a sausage. When she visits his office as a client, he takes the chance to make frequent secret visits to her home until one time when he finds her dead inside. He realizes he must uncover the true culprit to exonerate himself.

Byun noted this film sets itself apart from other thriller genre works as it also has a light-hearted sense throughout.

"The film is both easygoing and also brings laughter. It's a heavy topic but has a light sense to it, which makes it different from other thrillers," he said.

This film is the directorial debut for newcomer Kim Se-hwi, who took part in co-scripting the 2016 war action film "Operation Chromite."

A scene from the film "Following" / Courtesy of Content ZIO

The director shared she wanted to explore the human nature of self-rationalizing through two extreme characters — a stalker and an attention-seeker while delving into the very platform of social media that magnifies such nature.

"The theme I wanted to talk about was how humans tend to rationalize or justify their actions. Everyone tends to justify their behavior in some way for their own reasons. But illustrating that with someone unethical rather than ethical people felt like I could portray such instinct," the director said.

"Social media didn't trigger (such nature) but helped bring it to the surface … Since social media came out, we've been in a world where others look at us more favorably when we create a better version of ourselves (on social media). So I think the gap between the self I know and the one others see is getting bigger. And to fill in that gap, people tend to rationalize and justify themselves."

Actor Byun Yo-han / Courtesy of Content ZIO

Jeong-tae breaks into other people's homes but doesn't commit any malicious acts. He rather helps those he's stalking by doing chores like fixing pipes. Byun said he was drawn to such a unique character.

"I thought that the character of Jeong-tae was interesting because he claims he's just observing and helping, asserting he does no harm. And in the end, he admits he acted out of a sense of superiority. I was curious where that feeling came from," he said.

The story develops from Jeong-tae's perspective with his narration for the majority of the part. Byun said it was challenging to balance the character to be favorable enough as the protagonist, while not downplaying his wrongdoings.

"He convinces himself that he's a good man with a nice reputation. So I had to look at the script in two different ways, for the narration and his action … I can't make him completely abnormal and psycho from the start, so finding the balance was quite difficult," he said.

"I put a lot of effort to portray this character smartly, consulting with the director a lot … (With So-ra,) he might've felt like it was fate, or thought she was his type or was interested because her home was harder to break into. I actually analyzed a lot of backstories. So I prepared with various layers (of these backstories) and threw myself on the set to let it come out naturally when I saw So-ra."

The director, who revealed she has been a huge fan of Byun, expressed her satisfaction with the actor's portrayal of the tricky character.

"Jeong-tae secretly does bad things but believes he never crosses his own moral boundary. So it required exceptional acting skills to portray such a character," she said.

"When you just look at the script, there's a lot of blanks to the character, but Byun did a perfect job filling in those parts."