Jo is a mermaid labeled a sinner by her community because she jeopardized her life to assist her friend Ryuu in reuniting with a human, Yuki. However, Jo also falls for Yuki, leading all three to be captured. Jo finds herself imprisoned, while Yuki and Ryuu are held by Lord Harujion, who intends to exploit them to reclaim the seas and eventually human civilization. Yet, with Akira, a border guard skeptical of Harujion, can they liberate their companions and thwart his malicious plans?

A Sinner of the Deep Sea presents a unique version of The Little Mermaid story, reaching its finale in this volume. Although it may not hit the same peaks as the initial volume, I found myself appreciating it more than Volume 2, despite encountering similar issues in these chapters. Perhaps it’s due to my acclimatization to the changes in tone and pacing, but I also believe Jo’s increased involvement in this book, as opposed to her continuous fleeing and mishaps in Volume 2, contributes positively.

Volume 3 resumes from where the second concluded, with Jo imprisoned and Akira on guard duty…until she decides to aid Jo’s escape. Akira’s transformation throughout the series is well-executed. Her previously narrow perspective is gradually questioned across the books, and her disapproval of Lord Harujion’s grand scheme, leading her to back Jo despite the danger, forms a compelling character arc. She’s also resourceful, having connections Jo lacks, such as a sister working within the palace. With Akira’s comrades all part of the sea guard, they help shift the outcome in the final chapter, allowing her to effectively interact with the other established characters.

The problem with the main conflict is that, like the previous volume, a lot of the stakes and the plot pieces that end up playing a part in the enemy’s downfall, are only introduced in THIS volume. Lord Harujion’s special plans for Yuki and Ryuu are sinister but also just come out of nowhere, and the big reveal of the previous ruler being held captive this whole time, and being a massive part of the mermaids’ history is also info-dumped in this book. It’s a shame as a lot of these plot elements could have been introduced in the first volume. I loved the atmospheric and slow pace of the first volume, but if the mangaka wasn’t going to be able to keep that up, I would rather have had trimmed that and had a chapter to introduce the politics and history of this mermaid world properly, so that when this big threat and reveal came up, it wasn’t so out of left-field (or water in this case).

As for our heroine, Jo’s temper and proactive nature also make her a fun protagonist in this volume, although her hot-headedness does get her in trouble more often than not. She’s also very brave and willing to help her friends to the depths of the sea, and it’s her compassion and courage that end up winning the day. She gets a few hair and costume changes in this book too, including where she needs to dress up as a guard to sneak into the palace, which is a nice change of pace. You can see why Ryuu (her best friend) loves and trusts her, and why the human Yuki fell for her, even though I’m still not sold on his and Jo’s romance as a whole.

The art continues to be stellar and even though we don’t get as many awe-inspiring images as in the previous volumes, the panels are still gorgeous. The more action-filled chapters in this book are well paced and telegraphed, and the full monstrous form of a certain character is very detailed too. I also like the cover; the first volume’s cover depicts very dark, deep waters: Volume 2 is lighter blue, showing shallower seas, and now all the characters are on land, welcoming the orange sun. It’s a nice way to ‘show don’t tell’ how the characters have grown across the series.

Caleb Cook is again responsible for the translation which is easy to read and there’s a small translation note at the end, which is appreciated. There are also notes on the named sea mammals across the book, which is also nice to have.

I can’t say that the series ever truly recovers from its quality dip in Volume 2, but I can say that Volume 3 is a satisfying read that concludes the story well enough and visually, it’s one of the best looking manga you could purchase from your bookshop right now. If you like mermaid tales, and don’t mind the choppy waters that the story can take you into, it’s worth at least one read through.

Our review copy was supplied by Yen Press.