Well that was just a little heavy-handed.

Kaikisen: Return to the Sea falls into a classic trap. Is the greedy land-developer character not perceptibly evil enough despite the fact that he literally wears sunglasses indoors? Let's also have his driver almost hit the main character in his fancy car then, just to show that he really isn't someone who cares. It should be enough to let the motives and major actions of your characters speak for themselves, but sometimes authors just can't resist adding that extra little "kick."

Yes, our villain actually kicks a dog.

The absurd portrayal of the people behind the development project ruins what what would have otherwise been a relatively reasonable portrayal of the trade-offs between sticking to tradition and accepting modernization. (Well, it would be a little biased still, but we can accept that fiction in general has an inescapable fondness for the days of yore.) Instead, what we get is some hackneyed pseudo-profound mash-up of "respect nature/tradition/something" and "Magic and Miracles are Real!"

The climax and conclusion of Kaikisen, I feel, are similarly poor. A poorly-integrated extended car chase and a gratuitous all-out brawl at a festival might be excused perhaps, but some things are unforgivable. Not only is the age-old (and just absolutely tiresome) trope of Faithful Dog Companion Frees Hero By Attacking Evildoer invoked, but a similarly cringe-worthy moment is when the main villain has a complete change of heart in the space of two pages. And how can we be so sure that he's a good guy now? Well, just look at how sympathetic he looks without his sunglasses! Clearly, the sunglasses had been controlling him all along.

All that said, there is one major redeeming quality. As others have mentioned, the art is superb both technically and stylistically, and the confident linework, solid panelling, and careful shading and texturing can feel like a clinic in how to actually draw manga that looks good. Stylistically it's nothing to write home about, but that's just fine. Not everything needs to look like Gogo Monster or not simple, and if I were to borrow for just a moment that good old MAL system of assigning sub-scores for art, characters, and et cetera, I'd give this a full 10 in that category. First and foremost, the particularly strong art saves Kaikisen from being an unengaging read, but it is also valuable in one other notable respect. The subtly expressive way in which figures are sometimes drawn by mangaka can bring instant yet meaningful characterization to a character if done properly, and some of the best characters of this manga are not the main characters, with the exception of Natsumi, but characters like Yosouke's father, the mermaid, and the less caricatured of the townfolk.

Ultimately, however, it is difficult for Kaikisen to save itself from its heavy-handed moralizing, and while enjoyable enough most of the time due to the excellent artwork, the shallow build-up and entirely empty conclusion will not leave very many readers satisfied.