The second Keroro Gunsou movie is another of those ventures of a long running popular shounen franchise into the film business. While based on the series it does establish a self-contained story which runs outside of the series main plot line and doesn't conflict with it (although this really isn't a problem with Keroro Gunsou, as there isn't one to begin with).
This time, the movie is all about Natsumi. The Hinata family, together with the Keroro Platoon, is invited to an island by Nishizawa. When they arrive on the island, Natsumi is being abducted by a pair of weird aliens, Meru and Maru - two Maronians. As it turns out Natsumi has been chosen by Meru to be his princess, for that he constructs a city below the ocean just for her, a dream city based on her memories. Meanwhile Keroro, Fuyuki and the others devise a plan to rescue her and save the Earth from consequences it faces if Natsumi should accept that proposal.
One thing is certain, this movie is fun. Not fun as in throwing a ton of obscure references at the viewers and building up the episode on it, but fun as in having a well constructed plot, touching themes that are aimed at families and perfectly understandable for everybody who watches the film. It is basically a film about family and being there for each other and that it does portray in a well condensed matter, following the basic structure of a written story and adding some of the usual comedy routines of the character cast.
The movie is also fun because of its presentation. Yamaguchi Susumu, who already handled the probably best episode of the series - 102, is here again on board as director and this is obvious from the very first minutes of the movie, as it displays a quite different feeling from the usual Keroro Gunsou series. The background animation and the many rotating camera scenes are particularly his forte and work much better with the more serious character portrayal in this movie. The storyboard, also by Yamaguchi does indeed match up very well with the directing, not only presenting the movie in a nice to follow matter but emphasising the key scenes, which the usual style wouldn't be able to pull of that easily. While there aren't many scenes that outstanding it does adjust very well to the overall theme and makes sure to not demand too much from the viewer. One scene did impress me a lot though, that is the lovely bike chase scene towards the end of the movie, which did remind me a lot of a similar scene in Keroro 102 (also Yamaguchi's work? sure seems so).
Another scene that made a good impression was the moment when Natsumi accepts Meru, the traditional background music with chimes cutting off into silence only to be interrupted by a few sound effects, was extremely fitting to the importance of the scene. A few scenes towards the end were presented in a similar style, relying on faster paced music though. Overall, while the music offers a broad variety, going through several musical genres, it isn't especially outstanding as a whole, the same goes for the sound effects and the two (or three if you count the English version of the Keroro march in the beginning of the movie) vocal songs used in the movie. They do establish a good atmosphere though, adding to the enjoyment of the film.
Overall it's a very nice family movie and it offers the best things from Keroro, which makes it a must for fans of the series as well. The plot doesn't offer many surprises and twists but is scripted nicely, following the usual pattern of story-telling, being backed up by a very good, even if heavily restricted, directing and storyboarding and a nice movie level animation. If you expect something out of the ordinary, like Hosoda's One Piece Movie 6, you will be disappointed, but if you want to have 70 minutes of fun with our frog invaders and/or see Natsumi in a gorgeous outfit, then you'll have lots of entertainment with this movie.