Yin and Yang is a Sgt. Frog fanfic written by author jlucydaisuke. Then there was a sequel. Then another sequel. Then it became a series, with all in all three sequels, three side stories, and two oneshots.
Yin and Yang is the first story. Kururu creates a Super Soldier using his and Giroro's DNA. Well, he attempts to anyways - the result is Kirere, who's subpar at everything except puzzles and mechanics. Deciding to raise her as a normal girl, Kururu introduces her to the platoon, who try to get used to the new addition to the team.
Consequences is the second story. Kirere befriends a bill dodging mechanic named Haruki, then gets kidnapped by a powerhungry Russian author, Nikolai Kezanstav. It includes the introduction of Romama, who harbors secrets as the captain of a mission gone wrong on Pekoponian a long, long ago.
We Are Not Alone is the third story. Romama's teammates are discovered to be alive, and the platoon helps Romama find them, more or less because they want help for the invasion. Along the way, secrets are uncovered, Kezanstav appears again, with a wrong teammates of Romama who wants revenge.
Paradise Is Where The Heart Is is the 'fourth story', but is really a collection of Slice of Life stories about the whole OC and non-OC cast. Well, as Slice of Life as you can get with a large cast, alien and human, and trouble brewing in every corner.
This story provides examples of:
- Alternate Universe: Several, both made by the author herself and by fans of the fic.
- Badass Bookworm: Fujuju seems like a quiet guy at first... Only to end up being a dangerous pyromaniac.
- Darker and Edgier: both 'Eliza - A side-story' and 'The Past has a Past, too...' depict events far darker than the ones of the main series, that usually tries to stay true to the spirit of the original series.
- Evil Counterpart: While not explicitly seen as such, Nikolai and Fuyuki are both occult-loving boy that met an alien.... only, it didn't end well for the alien, on Nikolai's part. Doesn't end too well for Nikolai either...
- First Girl Wins: Played straight at first. Romama and Kodada DO end up as a couple, but the pairing doesn't last too long.
- Has Two Daddies: Kirere, who is the biological daughter of Giroro and Kururu.
- House Husband: Fujuju cooks and cleans while his wife is busy presiding over the order of time.
- Interspecies Romance: Let's see... There's Mahihi and Daisy, Romama and Aya, Fujuju and Botan, Rokiki and Mora, Haruki and Lavi, Porara and Mois, and even Kirere and Hiroshi, for one story.
- Last of His Kind: Subverted. Rokiki first appeared as the last member of the Sankaku Tribe, only to discover that survivors remain scattered throughout the universe, and he's got a few descendants right here with him...
- Manchild: Haruki, who even looks younger than he is. Arguably Mahihi in flashbacks, and, of course, Keroro is Keroro.
- Mayfly–December Romance:
- Subverted with other inter-species relationship couples, as in their human form, Keronian ages the same rate as regular humans.
- Mistaken for Gay: Fujuju, who's a soft spoken House Husband.
- Mood Whiplash: Since chapters in "Paradise is Where The Heart Is" focus on different characters and plots, tone can also vary from chapter to chapter.
- Oblivious to Love: the Toro/Kire pairing is MADE of this trope, along with several canon pairings, such as Giro/Natsu, Kero/Tama, and of course Fuyu/Momo.
- Promoted to Parent: Lupapa is perhaps the most egregious example of this trope, having taken care of her seven siblings since her parents' death. Frannie Martin also underwent this towards Oliver and Maggie.
- Ret-Gone: The core theme of Episode 8 of 'Paradise is where the heart is'.
- Shout-Out: Oh so much.
- Doraemon, in the first lines of the first story
- Lupapa's design is based on Naruto's Kankurou, and her whole family are references to Naruto characters. Her name and thievery are based on Lupin III.
- The character of Fujuju pays heavy homage to Doctor Who. He's British, wears a scarf, lives in an old telephone box that's Bigger on the Inside, and astonishes his human friends with alien technology.
Fujuju: We're going to make [the telephone box] fly.Oliver: …Next thing I know you’ll be fighting trash cans and offering everyone jelly babies.
- Lampshaded once by Oliver.
- So does Botan, the Time Lord...er, Time Bender.
- The designs of twins Maggie and Oliver are loosely based on Rin and Len, while their sister Frannie's design is based on Miku.
- Silent Snarker: Romama, who lost his voice after years of not talking due to being in Kezanstav's mind control. He got better.
- Sixth Ranger: Kirere, after the first story, ends up becoming this for the Keroro Platoon.
- Stalker with a Crush:
- Romama, who secretly watches Aya's ballet practice from the rafters. Though now they have formally meet each other, he might not be one anymore...
- Also, Momoka towards Fuyuki, as is the norm.
- Teen Genius:
- Romama, who is already ranked Major at his age, for his fighting prowess.
- Kirere can also qualify, since she's building invasion weapons for the platoon already.
- Tokyo Is the Center of the Universe: Averted during the third fic: the members of the Romama Platoon are scattered all around the world. It may border Aliens in Cardiff in the case of Lupapa, given she ended up in the Amazon Rain forest.
- Younger Than They Look: Kirere, who is, time-wise, around three years old. Biologically, she's eleven, thanks to her dad's Aging Ray Gun.