This review is mostly for myself and specifically a friend of mine. Not that this review is "objective" or anything, I just wanted a more serious and strict analysis of the show. Cuz it is kind of a meme and inside joke that i like this series, but i rewatched it recently to actually check if i really liked it, or rather, if it's really unironically good. (Also, this review is purely on season 1, at the time of writing i havent rewatched season two. Also spoilers ig.)

tl;dr yeah, its pretty decent despite it's flaws. I feel like it's storytelling and themes are actually executed well in a lot of places. Although, the format shows it's age and the "fights" are anything but varried or well thought out, something that i really value in shows.

My full thoughts on the series will be represented mostly through character summaries, as this show really focuses on it's characters and the relations they have with others. I mean, it is a romance story first and foremost.

Lucia Nanami

Not the best person to be center stage.
Let's get the good parts out of the way, i really enjoy her struggle of who does Kaito really love, her as a person or her as a Mermaid. Her 2 forms are a great dynamic, the human form being a self concious airhead and her mermaid form being extremely confident and genuine, however literally a threat to her life, as in, if her identity is revealed she dies and turns into bubbles. For a love plot, it's a really engaging situation, building tension through it's potential consequences, and especially initially, puts Lucia in a really tight situation, since Kaito is head over heels in love with the Mermaid form, while remaining pretty... i guess vague is the best word to describe it, to her human form. Teasing her, doing confusingly direct things (that first kiss scene was a genuine shock tbh) and even in his inner dialouge, never understanding what Lucia is really up to. The way this relationship develops and how it interacts with another common theme, one's duty, will be detailed better in other character summaries, as admitidly...

(this is where the positives end)
... Lucia is rather annoying as a character. From the main trio, she's easily the least engaging, mostly cuz of her stupidity, her obsession with Kaito and rather melodramatic reactions to things. I mean, i guess it's endearing to some people, sometimes it's funny (sometimes not for the right reasons either), but a protagonist of a show should be carrying a little more than she does. The genuinely good parts of her come much later or they are snuffed out by repetition or dead air of the dreaded fiLlEr EpIsOdEs. Slice of life fans rejoice, as you get to see little to no character progression for most of the series... ehh, i'll comment a little closer to this once i cover the minor villains.

Kaito Domoto

Kaito is honestly the more interesting part of the main relationship.
To counter Lucia, let's get the bad parts of him out of the way first. His deus ex machina powers is overused and really uninteresting. It picks up once the main villain becomes more center stage, but even then, i'd say Kaito is the least interesting part of that. Kaito as a plot mechanic is pretty dumb just cuz magical girl animes HAVE to have a powerful boyfriend character ig.

Kaito as a character is a different story. While his love for Mermaid Lucia is pretty shallow, it luckily shys away from it as he slowly and noticibly starts to develop feelings for Human Lucia. For the first half of the story, he puts up a rather repeling front to everyone. Being the too-cool-fo'-school-surfer-brooo and the chill chick magnet. But, within his little performances, glimpses are shown of his inner dialouge which shows a lot more thinking and caring side of him. He wonders whats up with Lucia, he starts thinking if she's the Mermaid from his childhood and when his guard is down, he lashes out or does something shockingly weird (like i said, first kiss scene is wack). And the best part is, his facade and defensive attitude falls apart in the second part of the story, where more and more, he gets "blushy" and emberresed with regards to Lucia. Now, when he's dealing with more difficult stuff, like the truth about his parents, he has to rely on Lucia for support, which, points to her, it makes this relationship feel genuinely sweet. All climaxing in the final arc, where he ultimately chooses Human Lucia over Mermaid Lucia. If only he knew, huh?

Hanon and Rina

Imma try speedrunning these;

Hanon, slightly less dumb than Lucia and feels like a good BFF character. Her relationship is exteremly flat, but thankfully and appropriately, she has to accept that it doesn't work and makes it a bitter-sweet conclusion for this arc.
In conclusion, fuck season 2, they ruined it by having Tarou be randomly into her again despite the final arc.

Rina, awesome character. Refreshingly without a love interest, except that one weird episode where shes into Kaito. Her story revolves around regret for leaving a friend behind and shows a serious side to the show.
In conclusion, fuck season 2, i might remember it wrong but i think they ruined her with her random new love interest.

Hippo

Hippo, strangely the star of the secondary characters.
While initially primarilly used for comic relief, he later gets a really sweet side story with one of the minor villains, Yuri. His character focuses on one of the shows major elements, which is duty. For example Lucia has to come to terms that she is a Princess and that her love for Kaito is taboo and irresponsible, especially since their kingdoms are kinda, you know, FUCKED OVER BY THE VILLAINS. Hippo's gimick is that he's her strict reality check, but his _hippo_cracies usually drain the seriousness out of it. Kinda of a disadvantage if your whole character is a joke.

BUT THEN HE BE LIKE, LEMME HIT YOU WITH SOME FEELS!
Once his "human" form is revealed and the side story with Yuri begins, he ends up being torn up by it all. He's basically in the same situation as Lucia, except, his is probably even more taboo since he's trying to hook up with the literal enemy. And while Lucia, being Lucia, encourages him to chase his heart, to back up his theme of duty, with a heavy heart he has to reject Yuri, even tho Yuri doesn't buy it at all and equaly mature, accepts it as well. Again, sucker for bitter-sweet love stories.

Also, his powers and role as a guardian feels a lot more engaging than Kaitos ass-pull powers. Mostly cuz Hippo's powers are explained a lot earlier, but i digress.

The Dark Lovers

The Tom (from Tom and Jerry) of anime.
As everything is love themed, they themselves are purely motivated to please their Master/Crush, Gaito. They are sometimes very genuine about it, as they sacrifice their power to him at the end, turning them into stupid little animals for it. They aren't very competent at it tho. In fact, they aren't very competent in general.

As villains, they don't really bring any tension with them. 90% of the time, their plans are absolutely stupid and they get beaten the same way every single time. It's mindless and really stings when thats mostly what the show is about for like half the time. It's actually why, later when they become actual inside jokes and are taken less seriously, is when they actually become more interesting. Their constant failours, them being concious of it and the slice-of-life struggles with it is actually endearing. They're so poor and hopeless, you wanna root for them just cuz, like I said, it's kinda like seeing Tom fail to get that damn mouse all the time.

For them individually, Izuru is easily the worst of them. She's boring, flat and has nothing going for her.
Eriru is the butt of most jokes. She's annoyingly stupid, but actually starts being endearing when they stop being taken seriously.
Yuri is great, her getting fed up by Gaito's abuse and lashing out at humans just to vent is a great lead into her side story with Hippo. She easily the most emotionally engaging out of the 4.
Maria is great, as shes is most often an actual competent threat to the girls. Shame about Deus-Ex-Kaito, as he's mostly her foil. Also side note, shes also ironically the most competent with Gaito as well, based on the sexual-tension in every scene they're together in. Sadly, again, we also know she has no chance in that either, but I'll get to Sara later :))

Black Beauty Sisters

What!? Tense Fights?! In my Mermaid Melody?!
yeah, when these guys first hit the scene, shit got real. The mermaid basically had 0 real challange so far, they won 99% of their fights with ease. I guess this is a good time as any to bring up the "fighting system" of this anime. I mean... the songs are neat? if youre into that kind of music. But, yeah, the elephant in the room is starting to sweat, all the fights are recycled footage and a unique song or an evolution in songs is more rare than it should be. Which is a shame, cuz it can be interesting, on like a really shallow level.

The Black Beauty Sisters genuinely present a threat and introduce hints to something more engaging with the battle system by introducing songs of their own and actually WINNING sometimes. This sadly gets exteremely degraded once the filler sets in and their encounters start feeling like any other. However, the times when they feel genuinely badass vastly outnumber the dark lovers and their plans contain like at least 60 iq points (sometimes)

The best part about them is their independancy. Unlike the dark lovers, they're loyal to Gaito mostly out of trust in his abilities. They aren't in love with him in any way, they seem to be more... into each other for most of the time. So once Gaito starts falling appart cuz of Sara, they up and leave him, basically saying "Fuck this, we can do way better than him". Their betrayal is a good end to their arc and brings a coolish battle to boot.

Gaito

Pretty cool when on-screen.
He takes a while to get going, having only small bits of foreshadowing to snack on in the meanwhile. When he delivers tho, he's actually quite interesting. Again, with everything love themed, his motives revolve around the woman he loves, which who can blame him, after him imma go into why she's the best character ;)
At the end of the day, he doesn't feel toooo evil. His hatred of mermaids is justified as it was more his ancestors and his race that bound him to the lonely life he lived. He doesn't even instigate the plot himself, he's freed by Sara and follows her wishes to destroy humanity. His true goals lie in getting rid of his lonelyness by surrounding himself with his minions, Sara and later his long-lost brother Kaito (wouldn't that make Gaito 13 years old as well when the series starts?? ig a thing to consider for his sad backstory). When he promptly gets abbandoned and left alone by littelarly all of those, he rightfully snaps and decides to adopt Sara's bitterness and wants to go along with the whole destruction thing.

And, the bitter-sweet ending, probably clear what i think of it.

Sara

You thought Gaito was the main villain?

Sara serves as kind of like the true mastermind to the entire story. She was just another mermaid princess before and much like Lucia, she falls in love with a human. That human happens to be extremely mid and ups and leaves her so he "doesn't get into her way", that being in the way of her duty as a mermaid princess. I assume cuz of the risk of her dying if someone finds out? That whole bubble turning thing gets neglected a lot...
She isn't aware of this however and assumes he just left her cuz he doesn't love her anymore. This abandonment and the duty that stoping her from pursuiting her heart makes her snap, turning her hair black and making her super strong (she took on 6 other princesses on her own, unscratched, like jesus). She even says in one of her flashbacks, like "To hell with being a princess."
This makes her super bitter at everything, especially humans and.... ok, i know i said she's the best, but imma say that her motivations kinda feel out of her leauge. Like, I get being bitter at Tarou, but all of humanity? Guess it's her way of venting...
Anyways, to pursuit her revenge, she frees Gaito from his prison and acts as his emotional support. Basically putting her trust in Gaito to fulfill her wishes and not to leave her like Tarou did. Her mind still wonders towars Tarou, she starts seeking answers to why he left her, almost drowns him once along the way but ultimately settles with keeping him a piano-playing slave at the castle.

What i find fascinating about Sara is how the themes of duty and taboo love affects her in the exact opposite way it does someone like Lucia. Sara probably wasn't supported as well as Lucia was, which lead to her (singlehandedly?) destroying her own kingdom, probably killing a bunch too. Which, for an anime for little girls, is pretty dark (or it's just my wishfull thinking, idk).

And to bare all of her sins, atone for her regrets and to repsect her role as Gaito's only remaining guiding light, she chooses to die with him at the end. Absolutely perfect ending for a character.

Spitfire Round
Good:

• i couldn't cover it all, but theres a lot of sweet moments throught the show. The way it tells it's story is it dripfeeds dropplets of story over a long time, which for its own good, at least the story ends up being decent.
• some of the filler is genuinely fine. I wouldn't call it great, on average it's more bad than good and i think the story would benefit greatly without it, but it's entertaining at times.

(special shout out to the Nikora side plot, for a show that's pretty obnoxious with how it portrays it's romance, it's reffresing to see this more "adult" take on it)

• Majority of songs are pretty catchy. It's prolly more a taste thing, but I'm more a recriational virgin, so i happen to like them. Fav is definitely Sara's song, do i need more proff that she's my favourite character??
• One particular filler episode was so bad, it was good. I lost my shit laughing so much, they liker randomly interupted the story 5 times with a random insert song, it was so funny, i swear.

Bad:

• Yeah, that part about filler being good was just pitty points, most is really mediocore. I stuck through it cuz of the dripfeeding of story, which i guess counts for something, but only really shows it's age. Probably a huge turn off for most people, shows how much the anime has aged.
• The production value feels extremely cheap at places. Granted the animation picks up in the second half and *gasp, even includes new footage for the singing portions :OOOO

... the other 98% of the time, it looks nothing special and recycles way too much. Run of the mill magical girl anime, in short.

• For being such an important character, Tarou really rubbed me the wrong way. His justification for leaving sara is littelarly kept secret until the final hour and revealed so matter of fact-ly, lost most of it's impact it could've carried seeing how it was the whole fuckin' reason the story happened in the first place. For the rest of the time, he's a clueless dumbass who just allows little girls to flirt with him.

In short, fuck season 2.

• I mentioned this earlier, but the "fights" could be a lot more entertaining. They feel almost like a formality to a point, just a thing to fill in the 20 minute mark for the episode. Better set ups, more stakes and consequeces would've probably improved it. ~~And yes, i know, im asking a magical girl anime to be a battle shounen.~~

Conclusion
I think that, with better presentation and pacing, this show has so much unironically good things in it, it could be amazing. Now, it only really stands as an awkwardly old feeling little girl's anime following a format, trying to save every penny as not to starve. Which, I guess that's what it was made for at the time. Even still, I will rest assured that my love for the show isnt 100% memey and ironic and that it does have genuinely good things in it. It's as good as I remember, and one day i gotta check if season 2 is bad as a remember.

I'll see if thats worthy of a review or not.