The setup for this comedy by Mine Yoshizaki is simple: Fuyuki and his sister Natsumi accidentally capture a frog-like alien. He was sent as part of an advance invasion force, but due to his incompetence, he quickly loses his weapon and is abandoned by his planet. The kids want to make friends with the alien, and he agrees to play along so that he can scheme uninterrupted.
They treat Sgt. Frog as a pet, one that’s able to help with housework. They assume that, if handled with kindness, the frog will show his good character, but he’s essentially selfish. That’s mitigated only by his inability to successfully accomplish anything. The human characters are the usual manga stereotypes — the geeky boy with special knowledge and his schoolgirl sister, convenient for panty shots. Mom’s a manga editor who talks about the importance of character and makes in-jokes while the camera pans over her extremely lush figure.
The humor works because of Sgt. Keroro’s self-delusion. He clings to his military training as a security blanket, but his cuteness, as a walking talking frog, undercuts everything he tries. No one takes him seriously. And how can you blame them, when he washes dishes by splashing around in the sink with them?
There’s also the bipolar Momoka, a fellow student who has a crush on Fuyuki. She’s found Private Tamama, another member of the invasion force who, like his rescuer, flips from aggression to meekness in an instant. The private and the sergeant have an oddly affectionate relationship, when they’re not looking for the other members of their team.
The second volume introduces another army frog, the devilishly red Corporal Giroro. His violence temporarily disrupts the household, but soon he’s been adopted as well. When the three frogs work together, they manage to both build a secret headquarters and complete a sparkling New Year’s housecleaning. Their military plans don’t go as well, so they set out to find their intelligence officer, First Sergeant Kururu, a talented inventor who’s more interested in being a DJ.
In book three, the four frogs continue plotting, whether it’s to take over the radio airwaves or create a human-killing plague or to de-age Mom so she is mistaken for her son (!). Another favorite ploy is to manipulate the characters so the girls somehow end up in swimsuits or later, as magical goblin girls in tiger-striped bikinis. Angol Moa, a Lord of Terror princess who’s also somehow Keroro’s niece, shows up, and she and Tamama compete for Keroro’s love. She’s more cute naive girl window dressing, although she also contains unimaginable power.
Volume four continues the mayhem with drunken parties, snowball fights, cavity wars (yes, in teeth), and body-switching. Japanese cultural events like sports festivals and hot springs relaxation are visited in volume five, as are the more universal targets of birthdays and reality TV.
In volume six, the tables turn when the frogs get a message from headquarters promoting Tamama to commanding officer. The frogs also invade school when the swimming pool opens, where their behavior is particularly cute. It resembles synchronized swimming, only not in the pool. Other summer activities include a beach trip and a temple festival. The book wraps up with an odd little tale that can be described as “what if the kids never found Keroro?”
Volume seven introduces Koyuki, a transfer student who challenges Natsumi, previously the most physically accomplished in the class, and the fifth frog, Dororo. He’s been acting as a kind of ninja superhero, exposing other types of aliens hiding on earth, and his love of his adopted planet puts him at odds with his former squad.
After Koyuki moves in next door, in one of those sitcom-like conveniences that provides more story opportunities, she develops a crush on Natsumi that annoys Giroro, who has his own crush. Later, the frogs try to help a Cosmic Detective (and childhood friend) find a job during the recession in a story that winds up parodying action television shows.
By volume eight, the character chart at the beginning of the book resembles a particularly complicated spiderweb. The color insert, featuring a close-up of the very well-endowed mother in a bikini, similarly gives warning of the kind of material within. Although it’s not a focus, there’s a good bit of underwear flashing and bathtub scenes and excuses to put the girls in swimsuits, never so much as when neighbor Momoka decides she wants to work on being sexier.
Other chapters feature a superhero slugman who parodies Ultraman; demonstrate how the characters handle losing electricity on a hot day; show the frogs encountering a group of manga writers; send the frogs out to turn other animals into soldiers; and have the group outwit student reporters seeking evidence of aliens.
Volume nine opens with another hot springs vacation, only first there’s a girl/girl fight over who’s going to accompany the family. Momoka wants to flirt with Fuyuki and has lots of money for gadgets; Koyuki’s a ninja that’s in love with Natsumi. Together, they provide plenty of fan service.
Following stories are even sillier, with Fuyuki made younger and riding a flying carp; Dance Man using his magic powers to give people Afros; Tamama teaching a young boy to play better soccer in the rain; and the frogs creating vending machines.
The pranks of a vengeful ghost, upset at being forgotten about, open volume ten, followed by a parable of helpfulness and the frogs playing soccer. Then begins the lengthy story of a replacement platoon getting serious about invading the earth. Just when the final confrontation appears, the book ends with a “to be continued”.
Volume eleven has the aliens and humans facing off for control of Earth. (Fuyuki is dressed as typical Japanese schoolboy in shirt and tie, while his sister Natsumi has wound up in a swimsuit, of course.) After the threat is turned away, there’s a flashback showing how the ninja neighbor met her alien frog companion, and then a story focusing on Keroro’s love of building models. Two frog schoolkids show up to see more of the legend they’ve heard about, and it’s up to Mom to save the day — kids are kids in any race, apparently.
In volume twelve, things are back to normal after the near-destruction of the earth. There’s slapstick violence after weapons are banned, then frogs and humans bathe together. A series of seasonal stories feature watermelons, storm season, Halloween, and New Year’s.
I had thought that the series ends with book twelve, but it turns out that it’s scheduled to run for several more volumes. That wasn’t exactly happy news for me, because I’ve lost the excitement I found in the earlier books.
It’s hard for an absurdist comedy series to keep its freshness, and I’ve grown a little weary of the title repeating the same kinds of things that originally drew me to the book. Sgt. Frog, at this point, has a sprawling cast, many of which (especially the frogs) can be difficult to keep straight. That’s why I haven’t yet reviewed volume thirteen or volume fourteen.
At its best, though, exaggerated slapstick made for imaginative fun. The books are filled with allusions to other bits of geek culture, like Keroro’s hobby of building Gundam models or reading comics. Typical manga plots are twisted, such as having the characters visit a beach island, encounter ghosts, create age-changing machines, or tell horror stories.
Once the situation’s been established, individual chapters resemble sitcom episodes. The frogs mostly act like toddlers, fiendish kids who happen to have very cool technological toys. The concept and characters are flexible enough to do almost anything, from parody to nostalgia.