Proposing itself as an intimate look at a killer, Eri’s Murder Diary (2021) caught my attention among the many titles at Japan Film Fest Hamburg. Directed by newcomer Koji Degura, I was excited to take a deep dive into the mind of a killer and see what I would find.
What Is It About?
Looking to better understand the troubled life of a murderer, a writer reaches out to a psychiatrist to help him interpret the actions of convicted murderer Eri. The story unfolds through interviews, observations and the tale of the young woman’s plight as she conveyed it to the psychiatrist. Sadly, we learn that Eri’s fate is tied to a deeply rooted mental health problem that causes her to adapt in extreme ways to effectively avoid change.
What Worked?
Showing its hand up front by relating Eri suffering from ‘environmental dependency syndrome’, aka ‘zelig disease”, the production sets a high bar for itself in both navigating mental health and keeping audiences interest in spite of lacking mystery. Thankfully, the understanding of the syndrome is certain to pique interest as the viewer looking to Eri’s every movement to try to make sense of how her mental illness drives her – sometimes obvious, other times rather obscure. Creating a bizarre obsession with the protagonist, there is intrigue for the viewer to try to formulate how much of Eri’s actions are the product of a broken mind.
Given the complexity of Eri’s charchter, Mei Matsumoto gives an admirable performance juggling the eternal struggle of an inner turmoil turning into a determination to meet her desire to have full control of situations. A cold hearted killer, but one crafted out of necessity of feeding her mental disability, Matsumoto proves to have the perfect range to tackle such a complex persona. Consequently, it is hard not to have a minor level of sympathy even when Eri begins to saw away at the corpses of those she knows, a desperate bid to escape her crippling fears.
Admittedly, the technical aspects of the production are a bit rough, often limited by budget and cramped shooting locations. However, there is a certain extra layer of anxiety when considering Eri is living in a confined space with a man she may not actually love – more in love with the idea of normalcy a relationship conveys. Overall, the cinematography and sound design won’t wow anyone, but it is complementary enough to help humanize the troubled woman.

What Did Not Work?
Conveying mental health in a realistic manner has long been a fault within cinema, and Eri’s Murder Diary is no exception. Essentially, the idea of Zelig disease manifesting itself in this way seems rather far fetched with how the case often pops up tied to other mental health issues like ADHD, which forces some to attach onto other in order to better understand social cues and blend in. However, viewed as taking inspiration from the condition in order to create a killer, the production certainly succeeds in creating a truly unique character. Overall, mental health is utilized in a creative way to push the narrative, but it certainly does not feel realistic – an aspect that is always appreciated when done right.
Perhaps the greatest disappointment of the film comes from an abrupt conclusion that feels forced. Although not enough to ruin the overall experience, the hard stop just leaves a lot of questions unanswered and does not give proper closure.
Where Can I Watch It?
Eri’s Murder Diary is streaming as part of Japan Film Fest Hamburg. The film is available internationally via online streaming, you can buy tickets for the festival here!
Overall Thoughts
Koji Degura has crafted a unique, albeit slightly flawed, exploration of a killer with severe mental health issues. As such, I found myself drawn deeply into the psychosis of Eri and fascinated by her twisted reasoning to capture an unattainable sense of security. I am really excited to see how Degura develops as a filmmaker! Even though Eri’s Murder Diary is flawed, the experience truly is a one-of-a-kind from the serial killer genre.

More Film Festival Coverage:
We Put the World to Sleep is a 2025 found footage horror/faux documentary written and directed by AdrianȚofei, with additional writing by Duru Yücel. Filmed across 13 cities, villages, and… Many look to the upper echelons of society with a peculiar sense of awe, lives where money is no longer a concern is something that has drawn people into these… Stop right here! Before you dive into this review and find out how phenomenal Frogman Returns is, it is essential that you watch Frogman (2023) first, which is easy to… Content Warning: This film contains depictions of ne***philia. Bad Candy takes place in the town of New Salem during Halloween, where two radio DJ’s invite callers to share local myths…. Fabián Forte’s Legions, an Argentine horror-comedy that premiered at the 2022 edition of the Fantaspoa Film Festival, is a delightful concoction bound to please fans of Sam Raimi, Alex de la… Bodycam is a 2025 Canadian found footage horror film written and directed by Brandon Christensen, with additional writing from Ryan Christensen. Brandon is best known as the writer/director behind films…We Put the World to Sleep (2025) Film Review – Metaphysical Found Footage [Nightmares Film Festival 2025]
Dead and Beautiful (2021) Film Review – The Decadent Undead
Frogman Returns (2025) Film Review – The Citizen Kane of Amphibian Horror Movies [Unnamed Footage Festival]
Bad Candy (2021) Film Review- A Frightfest Halloween Anthology
Legions (2022) Movie Review – Aging Shaman vs. Self Help
Bodycam (2025) Film Review – You Took Something from Us [Nightmares Film Festival 2025]
