Riko and Rimu Mikogami are two twin daughters of a water flea-researching father and a pet caretaking mother. One day, while searching a cat that ran away, they get into the attic of their house and find 5 mysterious compact-looking machines named "Kirumins". When they do what the Kirumin machines told them, they transform into a catgirl and a bunny-girl (nope, not the sexy type). Later on, they are joined by Nagisa, their older sister that can turn into a dog girl, and Ken and Tamao, two of their friends in school, but while Ken can transform into a mouse boy, Tamao's Kirumin doesn't work, but his kirumin looks like a bird. Regardless, he makes up for it with his intelligence.
Together they form a detective club, in which they solve mysteries mostly revolving around animals, and thanks to their Kirumins, they can turn into animals and use their abilities to solve any case, as well as understanding the feelings of the other animals.
Meanwhile, a mysterious organization leaded by Misa Hatori and co-leaded by her daughter Kanon and her assistant Pars, is trying to attract other humans and bite them to become animalians; humans that turn into animals, as part of their "World Heritage Project", but what are their true intentions?
Provides examples of:
- 20 Minutes into the Future: Despite the show airing in 2009, the series takes place around 2014 and 2015, even though it doesn't look that different than then other than SLIGHTLY advanced technology, such as human-tracking GPS's or the hoverboards Ken and Tamao ride.
- Adaptational Nationality: The Korean dub changes the setting to Korea, most notable in episode 1, where Nagisa and Kasumi's traditional Japanese archery uniforms are changed to regular t-shirts.
- A Day in the Limelight: In episode 22, Arai, the racoon member of the Kibagumi, runs away after getting a harsh punishment by Misa.
- Alliterative Name: The detective club's name: "Kamihama Kirumins"
- Also, Kanon's Phantom Thief name: Beauty Bat.
- Alternative Foreign Theme Song: The Korean dub has plenty of these:
- here's the first opening
and the first ending. - and here's the second opening and the second ending.
- here's the first opening
- Animorphism: The basic description of animalians; humans who turn into animals.
- Attention Deficit... Ooh, Shiny!: In episode 18, right when Keiko was about to ambush Tamao, she gets distracted by a clothing stand.
- Also happens to Nagisa earlier in the same episode when she gets distracted by a seashell that Kanon (as Phantom Thief Beauty Bat) threw like a frisbee. Of course, this isn't surprising considering Nagisa's dog habits.
- Aw, Look! They Really Do Love Each Other: Riko's had her fights with Ken here and there, but there are times where she shows to actually care about him such as when they're both trapped inside a cave or when he exceeds the 99 second animal transformation limit.
- Beach Episode: The second Clip Show (episode 41) has Riko and Rimu talk about past events while staring at the sea and eating shaved ice.
- Episode 45 also takes place in the beach, where almost everyone is temporarily turned into animalians because of a gas sent by Futatsugi. Said gas only affected those with potential of becoming animalians in the future, which they do in the finale.
- Berserk Button: You mess with mice, you mess with Ken.
- Big Bad: Misa Hatori, leader of the World Heritage Project, AKA the animalian revolution.
- Big Fancy House: Maybe not that big, but definitely fancy, as in "Was the architect a little girl?"◊. The school, too◊.
- Blind Without 'Em: Rimu and Tamao need their Opaque Nerd Glasses for very good reason. When Rimu accidentally knocks her off her face when she's trying to dodge a booby trap in one episode, she's forced to get down on her hands and knees and start feeling around helplessly for them until she finds them.
- But Not Too Foreign: Hatori Kanon (the bat-girl) is from Eastern Europe, is blonde with green eyes, but has a completely Japanese name, and speak perfect Japanese.
- But Now I Must Go: In the end, Misa and Kanon decide to go back to Vladonia to have a talk with Mr. Hatori. Pars also goes to his home country to live with his wolf friends there.
- By the Power of Grayskull!: The Kamihama Kirumins need to say "Kirumin!" to transform into their Kigurumin Mode and "Nugumin!" to cancel it.
- Cat Girl. And dog girl. And rabbit girl. And bat girl. And that's only after two episodes.
- Catchphrase: Ken's "One shot with guts!" with "Guts!" being a shorter variation.
- Cats Are Mean: Even when she turns into one, Riko has her fair share of incidents with them.
- Clip Show: Episodes 29 and 41 are clip show episodes where Riko and Rimu talk about the previous things that have happened during those points.
- Cloudcuckoolander: Tamotsu, the Mikogamis' father, oftenly gets lost in himself while thinking of water fleas.
- Clueless Detective: The duo of detectives Oozeki and Komusubi usually fail at solving mysteries themselves.
- Comically Missing the Point: When Ken's dad and Riko's sisters find out that the two of them went inside the cave he was exploring, Nagisa was distracted with how much meat they should buy.Rimu: Ken-kun went to follow you with Riko-chan earlier, didn't he...?Mr. Inomata: What!? He left the store to follow me!? So that must mean he's inside the cave-Rimu: Cave...?Mr. Inomata: Oh man, it would've collapsed by now because of that elephant...Rimu: Elephant!?Mr. Inomata: Eh? I hope they're not trapped...Rimu: AAAHHH! Onee-chan!Nagisa: You're right, half a kilo might not be enough. Mr. Inomata, please make that three-fifths a kilo!Rimu: Who cares about the meat!? Something happened to Riko and Ken-kun!
- Dating Catwoman: In episode 45 we eventually find out that kibagumi member Kabaya is dating Rumiko, Riko's teacher, and isn't even planning on animalianizing her. They even end up married in the finale!
- Dark and Troubled Past: Pars. His entire family got shot by hunters and he was the only one left.
- Detective Animal: Given the title, it's expected. The protagonists use devices named "Kirumin", which makes them able to transform into animals. They use them to get clues a normal human couldn't get, as well as communicating with animals and understanding their feelings.
- Didn't See That Coming: In Episode 4, Doctor the Turtle was trying to help Tamao kiruminphose by guiding him to a video containing the secret of the Kirumins. However, what he didn't know was that the camera's battery went out before the recording finished, therefore leaving the video unfinished.
- Disproportionate Retribution: 18 years before the show's events, Futatsugi made a love letter for Haruka and entrusted Tamotsu to send it to her, but he forgot to write his name in the letter. Thus meaning he hates Tamotsu's guts because of a mistake FUTATSUGI HIMSELF made. Justified since in the end, Tamotsu DID get the girl.
- Egg MacGuffin: Tamao BECOMES this in episode 25 after trying to kiruminphose to save Rimu from falling off a canyon.
- Evolution Power-Up: At some point, when the Kirumins reach level two of their progress they can turn into a bigger version of their respective animal. It first happens to Riko in episode 18, where she transforms into a serval. This is referred as the "Kirubara effect".
- At some point they can also turn into a different animal completely, like Rimu turning into a platypus.
- Foreign Language Theme: Opening and ending in Thai, by Neko Jump.
- Gentle Giant: Rufus Schonberg, after turning back to human, looks extremely huge, and acts very polite.
- Gelatinous Encasement: The packing plant on the UFO starts by squirting gel over the victim to make sure they can't escape.
- Greater-Scope Villain: Futatsugi. He turned Kamihama into a jungle, tested animalian-turning gases into various locations, and used Misa's trust to get his plan in action.
- Half-Human Hybrid: Marianne Schonberg, the Mikogamis' grandmother, is an animalian who married a human, thus making Haruka a half-animalian AND the three sisters a one-quarter.
- Heel–Face Turn: Everyone involved in the Animalian Revolution turns on Futatsugi after learning the truth of him.
- Heroic BSoD: During episodes 38, 39 and 40, Ken starts feeling more and more depressed about not getting the Kirubara effect and not transforming into animals other than mice.
- Happened to Kanon in episode 48 after Ken, who went over the 99 minute limit, ran away from her.
- Hour of Power: Should the Kirumins turn into animals, they must turn back within 99 minutes, otherwise they'd stay in that form forever and even lose their human conciousness, thus turning them into normal animals.
- How Do I Shot Web?: while the initial transformations are simple enough, it takes a few episodes before the girls figure out how to transform completely.
- I Choose to Stay: In the finale, the Kibagumi decide to stay in Kamihama to live a happy life.
- Innocent Blue Eyes: Rimu, in the few instances where her eyes can be seen
- It's All My Fault: Rufus blames himself for choosing Mr. Hatori to be Misa/Michelle's wife, since he was the one who froze him in the Siberian mountains.
- Large Ham: While she's normally rather reserved, Kanon has her moments, such as her super villain persona.
- Last-Minute Hookup: Yuuki Mikogami finally turns back to human from his turtle form... right at the last scene of the whole show.
- Little Bit Beastly: pretty much the subject of the anime.
- Long-Lost Relative: In the finale, it's revealed that Kanon was the Mikogami sisters' cousin all along.
- Love Makes You Evil: The reason Futatsugi has grudge for Tamotsu is because he got his crush, Haruka, before him.
- Lyrical Dissonance: If the subtitles are to be believed, the seemingly upbeat title theme is about someone despairing at a dream they had that supposedly signifies a lifetime of solitude.
- Magic from Technology: The Kirumin compacts are completely created using science, but allow the protagonists to become Little Bit Beastly Magical Girls that can transform into the animals they're assigned.
- Magical Girl: Unlike most anime with these, this show's team also has a huge age gap between its members (two kids and a teenager). It's not the first instance in animé history, though (that honor goes to Sailor Moon). The team later add a boy into their team, who arguably becomes the show's protagonist with his drive for detective work, which is what most of the show is about.
- Magic Pants: Slightly averted. The girls are left without their clothes right after they un-transform, which float down from nowhere soon after.
- The Mind Is The Plaything Of The Body: Everyone has their moments, though Riko is the most noticeable, ranging from trying to eat Ken when he first turns into a mouse, to unintentional acts of catness even when she isn't transformed.
- Mythology Gag: Some of the obstacles in Futatsugi's underground maze in episode 49 are based on some of the scenes from the opening.
- Neat Freak: Arai is obsessed with cleaning.
- New Job as the Plot Demands: Abe, a guy with an orange headband appears every so often through the show, always with a different job.
- No, Mr. Bond, I Expect You to Dine: Inverted. In episode 42, Haruka invites herself to Misa's castle to have a little talk with her.
- Older Than He Looks/Younger Than He Looks: Oozeki is 48 years old and Komusubi is 26, yet they look like as if they were vice-versa so much that the police leader confused them for eachother.
- Puppy-Dog Eyes: Nagisa pulls this on Ken when they need his help for something. Bonus points for being part puppy while she does it.
- Secret-Keeper: Haruka, the mother of the three sisters, knows very well about the kirumins since the start, and is willing to give advice to the detective club while keeping their secret.
- Shipper on Deck: Kasumi appears to be a big Nagisa x Pars shipper, sometimes acting as The Matchmaker for the both of them.
- Sibling Yin-Yang: Riko the extrovert catgirl; Rimu the introvert rabbit-girl.
- Stalker with a Crush: Kanon is obsessed with Ken, and she always tries turn him into a bat animalian.
- Temporary Love Interest: One episode has Kasumi falling in love with Handa. She eventually gets over him because she isn't interested in the attractive boy type.
- ...and then by episode 45 she falls in love again. Unfortunately for her Handa doesn't remember her at all.
- The Call Put Me on Hold: Despite having his own Transformation Trinket, Tamao is unable to transform during early on the series. He finally gets to kiruminphose by episode 27.
- The Faceless: We never get to see how Kanon's father looks like, there was just one scene where Kanon had a phone call from him. We do, however, get to see his animal form: a Pegasus.
- The Man Behind the Man: Rufus Schonberg, Kanon's grandfather, was the one who created the animalian revolution. Misa simply took over while he was hibernating in his coffin.
- Vile Villain, Laughable Lackey: Misa Hatori is very serious about her World Heritage project, but her henchmen, the Kibagumi, are a bunch of idiots who can't bite more than one single woman.
- There's Keiko, who is a massive goofball who can get easily distracted.
- Villainous Rescue: In episode 26, Kanon saves Riko from being trapped in the box with the other captured animals.
- Voluntary Shapeshifting: Animalians have the power to do so. However, sometimes when an average human becomes an animalian, they don't transform so voluntarily at first, and they don't even remember turning into one after turning back.
- "Where Are They Now?" Epilogue: Episode 50 replaces all the pictures in the ending with pictures of what happened to all characters after the end.
