The most underrated anime I know of is Marmalade Boy.
Marmalade Boy was originally an 8-volume series by Wataru Yoshizumi, and the anime adaptian aired from 1994-1995. Yeah, it's old, and and frankly, you can tell by the animation. XD The dub was done by Tokyopop, and despite it being old and the animation suffering because of it, I think it's extremely underrated.
It's a shoujo series, but it's not the typical kind of show you see. The premise is good for those who like romantic comedies that are well-seasoned with drama (I'd reccommend it for fans of Peach Girl, Mamotte! Lollipop, Lucky Star, and Ouran High School Host Club).
The basic plot of the show is as follows: Teenager Miki Koishikawa has always had a relatively normal life. She's attends the local high school, hangs out with her best friend Meiko Akizuki, and is in pretty much every way, average. One day, her whole life is changed when her parents tell her they're getting divorced. That's not all though. They're getting divorced AND swapping partners with another couple who is getting a divorce. Miki is flabbergasted as they tell her this with a straight face. Infuriated that her parents are getting divorced so casually after being happily married (or so she thought) for so long, she is at a loss as to what to do.
The next night she meets the couple her parents are swapping partners with- the Matsuuras. She sits down to meet them when their son walks in, and just so happens to be Miki's age (Yuu Matsuura). Miki is elated, thinking her and Yuu can team up and stop their parents from getting divorced! You'd think this would be the main plot of the show, but by the end of episode 1 you find out that is not the case. Yuu doesn't even seem to care that their parents are just swapping partners. Miki then throws a fit, not wanting her parents to separate or for her to choose sides. Then it is revealed that Miki's parents don't expect her to choose. This bizarre situation gets even weirder when they tell her that both couples are going to move into one house together! So Miki finds herself moving in with the Matsuura's and adjusting to this wacky scenario. This is the set-up for the show.
The rest of the series is her life with this family arrangement. She has to learn to accept it, and perhaps find love on the way. I really like Miki in this series, because she's very "real". She's not some sweet, girly girl. She can have a temper, and is known to overreact sometimes. She acts like a real high school girl would most of the time. xD The characters in general are pretty good. Some of the characters get a little too close to cookie cutter for my liking, but for the most part the character are interesting and unique in their own way.
The voice acting isn't too bad for an older series, and the lead role is voiced by Michelle Ruff (Tsukasa Hiiragi in Lucky Star, Yuki Nagato in The Melancholy of Haruhi Suzumiya, and many other roles). Most of the VA's aren't too well known, but they are pretty good voice actors nonetheless.
The anime is very "shoujo", as it is a romantic "dramady". It has comedic moments, but it never really "tries" to be funny. Since the premise is so bizarre, that alone makes it humorous at some points. To be honest, the most hilarious element of the show is the four parents. They just act so bizarre (often talking in unison, acting more childish than Miki and Yuu), and sometimes their parenting is questionable (leaving Miki and Yuu home alone so the four can go on a vacation together) that they provide a few laughs. Besides that, the show mainly rides on its drama. There are many romance series cliches (the ex-girlfriend, the childhood friend, etc), but some of the situations are fresh for its time, and there are some scenarios I'm yet to see in another anime.
Overall it's a great dramatic romance series with a bit of comedy here and there. Way underrated. If you can get past the mediocre animation it's a good show. The series is 76 episodes long and is available in 4 box sets.
+See Costume List for Completed Projects+
+Rarity+ MLP:FiM ~100%~ Just finished!
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+Ciel Phantomhive (Vol. 6 Outfit)+ Black Butler
+Hatsune Miku (Snow Version 2013)+ Vocaloid
+Conventions Planned for 2013+
Sakura Con 2013 ~ 65% Likely
Everfree 2013 ~ 30% Likely
Kumori Con 2013 ~ 40% Likely
Aki Con 2013 ~ 100% Likely