Mermaid Saga was written over the course of many years: one chapter here, and one chapter there. Therefore, since it was not a constant publication, Takahashi did not face the same pressures that she did with many of her other works wherein she had to publish the next installment before a deadline. This translated into a very concise and well written short manga that properly does its job of offering the reader a glimpse into the strange and ultimately sorrowful lives of Mana and Yuta.
Mermaid Saga is a story set in Japan and jumps timelines from time to time. For the most part, the story takes place during 1980ish Japan (the time period during which this manga was published), however there are flashbacks and entire stories set in other historical periods, like during the Tokugawa Shogunate era. In this series, there is a legend: he/she who eats mermaid flesh is granted immortality. However, as we learn in the first volume, not everyone survives the transformation. Only one person in many will be granted full immortality. Some may be granted it on a temporary basis, meaning that they may wither away eventually and die. Others may not even survive the transformation; the mermaid flesh corrupts them and they turn into a "Lost Soul", a grotesque animal-like being with no soul. Additionally, the legend also applies in the reverse: A mermaid who eats the flesh of a human will be allowed to live on land as one (and consequently also takes on the likeliness of the human whose flesh she has eaten.)
The story focuses primarily on Yuta, who has been alive for 500 years. He is tired of living and hopes to find a living mermaid so that his immortality may hopefully be reversed. He wants to grow old and enjoy life as he was meant too, not necessarily die on the spot (because it turns out that even if you're immortal, you do have a weak spot. If someone were to cut off Yuta's head cleanly off his body, he would no longer come back to life). On one such journey, he stumbles on a village hidden in the mountains where only women live. Here he finds a young girl named Mana and after realizing that all of the older women in the village are mermaids, he tries to save Mana as they had been raising her in order to eat her flesh and stay as young beautiful girls on land. By the time Yuta arrives, Mana has already eaten the mermaid flesh so she is immortal as well. By the end of the story, Yuta learns that one of the women was not a mermaid - she was an immortal human who chose to live with the mermaids, thinking that it was the only place a "wretched being" such as herself could belong.
From there, Yuta and Mana begin to travel together. They stumble upon various cases where the myth of the mermaid flesh has ruined people, bringing them great pain and sorrow. Whether it was the mermaid's ashes or the mermaid's blood - they all had some effect that ultimately caused pain for whomever consumed them. I think the most disturbing story for me was one of the last ones, the story of Masato. Seriously, it has many twists and turns and by the end not only was I severely disturbed but I understood the impact that desiring something so impossible can have on people.
Overall, each short story was just as enjoyable as the last. I will admit that it's a dark manga, but it really delves into the human psyche and the soul, explaining that whether by choice, or by accident, living forever causes more sorrow than happiness. While a final "conclusion" of likes is never reached, I found it strangely satisfying. I think that in the end, Takahashi was trying to explain that a mermaid seeks long lasting youth and beauty above all else and therefore, would not help someone who has obtained it, lose it. Takahashi's mermaids are narcissists and even if Yuta were to be able to speak to one, I believe that the mermaid would grow angry for his rejection of the "gift" and either refuse to help him or try to kill him. I like to imagine that Yuta and Mana may still be traveling the world together, encountering people who have suffered due to this myth of immortality, a myth that many continue to not only believe in, but long for today.
p.s. This manga is also an anime! I may eventually watch it, but no promises. I tend to get queasy when watching dark/macabre mangas in an anime format >.<