Brigadoon: Marin & Melan/YMMV

Arc Fatigue: This troper can't be the only person who got really sick of the whole "betrayal" thing with the Gun-Swordsmen, right? It just got stretched out way, way too long. It wouldn't be so bad if we got to see Melan and his friends finally get over this and act like the team they're supposed to be for more than one scene. It would have been even better if they actually got to fight the Final Battle.
Esoteric Happy Ending: If you think that Marin goes to Brigadoon with Melan at the end, that's a truly strange ending. What kind of future can there be for a thirteen-year-old human and an alien robot?
- Not to mention the fact that some of the villains namely Kuston and Lulu/Aloma are still alive and could potentially still cause some problems.
Iron Woobie: Melan endures all kinds of punishment without complaint.
Needs More Love: Like you wouldn't believe.
So Bad It's Good: The english dub. The voice acting is adequate but hilarious.
Squick: Oh, where to begin...
- Marin's frequent panty shots and nudity might be less disconcerting if she wasn't only thirteen years old.
- Melan as Fetish Fuel. Yeah, he's hot and all, but he's still an alien killing machine from another planet.
- Marin and Melan's romance. Not only is it an Interspecies Romance, but there is a MASSIVE age gap between the two.
- Marin and Moe's Romantic Two-Girl Friendship. Even if it's played for laughs, there's some scenes and lines that are a little too suggestive.
Subbing Versus Dubbing: The Japanese voice cast has better chemistry than the English dub that was cast well but doesn't leave as much of an imprint as the original.
Tastes Like Diabetes: The super-cute ending theme doesn't feel appropriate to the Darker and Edgier tone the series soon takes on, and can frequently be a source of Mood Whiplash.
- The second volume of the soundtrack has Marin and Moe singing a duet version of the song, and includes some of their fluffy friendshippy dialogue from the show. So sweet it can cause cavities!
The Untwist: The true identity of the Big Bad might come as a shock to some or a disappointing anticlimax to others.
- Aloma and Lulu's similarities are so painfully obvious; they couldn't possibly be the same person. Nor could Lulu be behind Brigadoon's troubles. But he is.
- There's so much of this in the final episode that it's ridiculous. First we have Chroma showing up with a new batch of Reikons just in time. Then there's also the fact that Marin turns out to be stronger than Creis Marine, allowing her to be The Chosen one after all. And then out of nowhere, Aloma gives The Reveal that Marin is Creis Marine's prototype and thus her ancestor, but it doesn't answer any questions about Marin's true origins.
What Do You Mean It's Not for Kids?: See the Squick examples, plus Overdrawn At the Blood Bank, Humans Are the Real Monsters, Kids Are Cruel, and Sliding Scale of Idealism Versus Cynicism.
Woobie: Marin. She suffers so much due to circumstances outside of her control it's impossible not to feel sympathy for her. Moe qualifies for this as well, especially when she's the victim of a Monomakia that causes her to uncontrollably grow bigger until she is in danger of exploding. Melan counts, too, though in his case he's more of an Iron Woobie.