If it's possible for a show that's relatively dark from the beginning to have a Knight of Cerebus, Sujigarano Akumaro would qualify. The Gedoushu at large wanted to create enough anguish to cause the Sanzu River to rise high enough to flood the world of the living, thus enabling their incursion thereof. Akumaro, on the other hand, wanted to open a portal to Hell because he wanted to enjoy absolute human suffering — even though said opening would destroy both the human world and the Sanzu River. He also made Fuwa Juzo's sword from Juzo's dead parents, whom he murdered himself. His monstrosity extends to even the Ayakashi who serve under him; they seem specifically made to cause as much suffering as possible in order to further his goal (using said suffering as a wedge into one of six precise points along a line, at the center of which was a portal to Hell).
Fuwa Juzo was a remorseless Blood Knight to the point that even his fellow Gedoushu didn't trust him; he even only became a Gedoushu in the first place so that he could keep killing in spite of his sickness. Akumaro saw potential in him for his ability to walk the line between humanity and the Gedoushu and sought to use him to open the gates of Hell. However, he throws a sharp wrench into the plan, declaring that he already knew that his sword made by Akumaro was made of his parents (a fact which Akumaro had recently told him to bring him to a Despair Event Horizon), and that he didn't care.
Genta has his own theme song, aptly namedIkkan Kenjou! Shinken Gold. Not highly upbeat but it fits his character well, mainly because a good part of the lyrics is lots of vocabularies directly related to himnote "Electronic Mojikara", "Ikkan Kenjo", "The Clap of Victory",..., and it was especially cool while playing during his first battle in Act 17.
And the grandly Hot-Blooded theme song of SamuraiHaOh: "The Ultimate SamuraiHaOh Descends!". Give it a go here. WarningAudiences may be subjected to godly levels of heat, shouting and epicness.
For whenever someone is at the utmost seriousness: "Bushido Icchokusen", a.k.a: "that little tune".
How about ShinkenRed kicking Nanashi ass right on Act 1, to the tune of the main theme? Granted, it was a kind of a replacement to the standard opening sequence (maybe because the other four core Shinkengers were still about to be introduced), but it still looked and sounded cool like heck.
The ending theme to Shinkenger VS Go-onger: "Samurai First Rap ~Ginmaku BANG!!~", basically the Shinkenger version of Go-onger's Dancing Theme ending. What adds to the music is all six Shinkengers dancing in the ending credits. It's slightly surreal, to say the least; especially Takeru dancing.
Warning: If you're familiar with the glossary in Shinkenger, you'll find it an Ear Worm. If you're familiar with the characters, you'll find the ending sequence an unstoppable Ear Worm/Eye Worm. If both, meet your new drug.
Then there's To e! Shinkenger which plays whenever one of the Shinkengers is about to kick some serious ass.
Dull Surprise: While not as bad as her Western counterpart, Mako has moments of this. One particular moment was when Dayu drew her sword at her, and she responded with indifference.
Ear Worm: The opening theme is plenty good, but the part that really sticks to the ears is the "Chan-chan-bara chan-barabara...".
The ending song, with its "Wasshoi!", "Hai" and "Ya, ya, ya!", is pretty catchy too. If you don't end up chanting along with the bridge, you've got a stronger will than a lot of of your fellow tropers.
Ensemble Darkhorse: The reason for Kaoru's rising popularity is because of her being a character who appeared in the very end of the series. She's a breakthrough concept that's done quite well (first female Red ever).
Fan Nickname: "Marijuana Man" for Ryunosuke, especially for people who don't initially recognize the Kanji for water and confuse his visor for that of a cannabis leaf. "Aibaranger" is often used as well, due to the popularity of his actor, Aiba Hiroki.
"Ham Sandwich": Appropriately named for the duo of Ryunosuke and Genta.
Fan-Preferred Couple: Takeru and Mako. There were some episodes where Mako conversed with Takeru about things and helped him out (such as the episode visiting the island full of brainwashed people), and ALSO the episode where Mako posed as a bride for Takeru. But otherwise, Mako pretty much treats him like either a Lord or her being the Cool Big Sis figure. Of course, since when did that stop the shipper?
And not to mention there's JUST as much of fans that prefer the Takeru and Kotoha pair, because of just how... dedicated Kotoha is to Takeru, and how Takeru seemed to either appreciate her presence, 'borrows' her Shinkenmaru a lot if he needs a spare, and he once played butler to her. Again, since when did this stop the shipper?
Two Kamen Rider Decade movies would use the phrase "ika (squid) de beer" as an Incredibly Lame Pun for the Showa-era MotW IkaDevil. What are Dokoku and Shitari best known for? One's a squid and one's an alcoholic, of course. This point would get hammered home in the Shinkenger V-Cinema as Dokoku and Shitari's voice actors appear in person, holding a sake cup and dried squid respectively.
It's debatable whether this goes into Harsher or Hilarious but here goes: In episode 40 "The Sent Words", Kotoha thinks she's a substitute for her older sister until Hikoma points out the word "substitute" was never mentioned and that her sister and him thought she was the true and only Shiken Yellow. The 'Hilarious in Hindsight' part comes a little over a year later when Luka becomes Shinken Yellow. 'Harsher' comes in when you realize/remember how Luka got the Shinken Yellow power, but 'Hilarious' returns because Gokaiger's finale and the Super Hero Taisen film (Super Sentai with Kamen Rider) make it obvious that Kotoha got her powers back, making Luka Kotoha's substitute.
Remember episode two when Ryunosuke/Shinken Blue tried to combine the Origami into a combined mecha by stacking them on top of each other? Well, guess how the Zyuohgers combine their Cube Animals into a combined mecha? And then consider how Kotoha mentioned that their gattai looks like an oden skewer, when the Zyuoh King completes its transformation by having a spear skewer the cubes!
Act 43: Juzo appears to go along with Akumaro's plan, but at the last second, he turns and reverse-blade slashes Akumaro, then shatters the breaking point bewteen Earth and Hell, denying forever the one thing Akumaro has ever wanted. And the reason why his entire Evil Plan failed? Because he cares more about killing people than about Akumaro's Hell on Earth or the soul of his former lover.
If what Dayu pulls at the end of Act 47 doesn't double the HSQ for the entire series...
Forget Dayu. Uramasa stabbing Juzo in the foot, taking the form of his former lover, and then erupting into flames not only qualifies as HSQ but as one of the most spectacular deaths of any Sentai villain.
And Act 48 beats all of the above with the Rokumon Junk sailing out of a crevice as the Sanzu River floods Japan.
It Was His Sled: Being a huge twist near the end of the series, the existence of another Shinken Red is pretty common knowledge.
Launcher of a Thousand Ships: Takeru must be the Lord of Black Dresses here. He has unique relationships with all his vassals, which is very much Shipping fuel, not to mention quite a bit of Foe Yay with Juzo.
The entire cast is shippable, even if not with every single character. Observe this excerpt from TV-Nihon forums.
User A: "...every 2 episodes it seems like everyone's being paired with someone else."
Kotoha idolizes Mako very much and is close to her. While this may be also seen as being a very close friend, in Shinkenger Returns, Kotoha's fantasy is being a girl disguised as a boy in an all boys school to be with the "guy" she idolizes and loves. Since guy is in quotations, no cookie for guessing Mako is playing Kotoha's character's crush.
Memetic Mutation: Ever since Kaoru adopted Takeru, fan artists have become very fond of making ridiculous scenes of her trying to act like a mother. (One had her attempt to give Takeru a bath. Another had her trying to play matchmaker).
Moral Event Horizon: In Act 34, the Nanashi attack an elementary school, kidnap the kids that study there, and then they are tricked into piling rocks under the promise that, if the pile is high enough, the children will be allowed to see their parents again. As if that wasn't enough, Akumaro puts some Nanashi there with the little kiddies just to knock their rock piles down over and over again (if you read it all attentively, you'll see that this last part doesn't fall under Arson, Murder, and Jaywalking). Yep, Akumaro's that brand of dick.
It gets "better" - the scene is a re-enactment of the afterlife in Japanese folklore. Specifically, the punishment given to stillborn children in purgatory. And you thought it couldn't get worse.
Any hopes of Juzo's redemption gets slashed when he made it clear that even if his the souls of his family sealed in Uramasa want him to stop being a Blood Knight, he doesn't give a shit - all he wants to do is kill with Uramasa!
Narm: SamuraiHaoh's Daishinken Daikaiten Giri in Act 41, which is likened to a brick spinning in mid-air thanks to it's terribly massive size.
Nightmare Fuel: Act 27. Just... ask Genta. He got his soul transferred to a sushi and was about to get eaten by a cat, only to be saved in the nick of the time. The experience traumatized him so bad, he couldn't transform into Shinken Gold because the sushi phone reminds him of the cat; he even had trouble just touching the phone. It would have been a really serious affair, if the phobia wasn't fixed in a few seconds.
One of the victims had a similar experience in that Act. Her soul was swapped into an empty soda can and nearly saw herself get crushed had Chiaki and Kotoha not forced the Ayakashi to release all the souls he transferred.
The Ayakashi in Act 41 has the ability to cause unsatiable hunger or thirst to anyone covered in his black sand. It doesn't reach the point of I'm a Humanitarian with the exception of Genta trying to eat DaiGoyo's head.note By the way, did we mention that Genta's... expression at the moment could beat the shit out of Gunpei'sraepface◊? Take a look.And yet, while most of the victims are eating normal food, it's so painful to watch the victims go insane for food and water, and those unlucky enough to find any look like they're about to die. Mako's desperate screams for water as if she was on the verge of deathreally didn't help... Oh, and the more you eat/drink, the more you hunger/thirst.
In Act 42, the Ayakashi has the ability to unleash and a swarm of bugs that fly into the victim's mouth and cause extreme pain. And most of these instances are apparently leading up to Hell on Earth.
The Scrappy: Tanba. At least Kaoru's rescue from the heap was successful as she was welcomed warmly when she returned in Kaizoku Sentai Gokaiger and has had some fan following on her own. Tanba reverts back to his Jerkass persona and throws himself back in. In his defense though, he lightened up with the Takeru's generation because he grew to respect them. The Gokaigers are nothing more than pirates that just took the Shinkenger's power, defaming generations of Shinkengers.
Values Dissonance: A lot of American and European tropers find themselves invoking What Do You Mean, It's for Kids? when watching Shinkenger. For a general-audience series, Shinkenger doesn't shy away from implied violence, and even death, of civilians by Gedoushu; also, the references to Japanese Myth invoked can seem as rather dark for a kids show. Often results in some Nightmare Fuel, so see that entry as well - oh, and some of it's high octane.
The Sake Dokoku's been chugging down like water is made from/of humans' fear and despairnote Either directly, or from the Sanzu water used in making it.. So, he's trying to torment all those people basically just to keep his tank full and gain some real estate. What a nice guy.
Ayakashi attacks can also have varying amounts: Instead of killing the victims outright, they let them suffer for as long as possible, or until the Shinkengers cut them down. Considering most of their methods are, in principal, fantasized versions of torture and psychological attacks possible in real life... makes things actually much creepier.
Just narrowly averted in Act 38: When the newly trained Nanashi Rifle Squad appeared in the human world, the Ayakashi in charge decided to try target practice on "moving targets". Good thing the Shinkengers arrived in the nick of time.
Hell, the number of cuts and bruises the Shinkengers can get in a normal fight serve as constant reminders of one meaning of Shinken; the fight scenes are goddamn serious.
Act 42 is the embodiment of this. The fact that Akumaro wants to create Hell on Earth already qualifies, but doing so involves destroying both the human world and the Sanzu River making him an Omnicidal Maniac. And let's not forget that Akumaro reveals that Juzo's Uramasa was created out of the corpses of his own family!