After seeing a couple of theories surrounding Reki's red hair as well as a headcanon theory on one of Kaoru's and Kojiro's skating friends who also had red hair, I'm inspired to share my headcanon too, but what started off as a solely Kiriko post developed into what I dub:
Or alternatively: "why are there so many gingers in this goddamn show!?"
Huge disclaimer: Most of this is just hypothetical as we are talking about anime logic and hair colours here (even if some parts are backed by analysis and evidence from the show). Only read it for fun. I apologise if it gets long-winded.
Tagging @argushatesplanes, @ihatethepersonwhochosemylastuser, @dixionduckling and @painfullyideal since they started this first and are my inspirations.
Part 1: Why the red hair?
It's a pretty known fact that our main protagonist Kyan Reki is a redhead, and so is the most important female character in the entire show Kamata Kiriko, even if it's a darker red.
The simple answer to why Kiriko has dark red hair is that she is related to the Kyan family in some shape or form. Maybe she doesn't have to be, not all redheads are related to each other.
But personally, I'm not too excited about family relations. I'm more interested in parallels and themes and all that lovely storytelling stuff.
What Reki and Kiriko really have in common other than their red hair... is that they are both enemies to Adam/Shindo Ainosuke.
The way Reki & Kiriko were antagonised against Adam in the show are different from other characters: Cherry and Joe were Adam's old friends, Miya and Langa were groomed by Adam, and Tadashi is his dog childhood friend and secretary.
They represent the antagonistic forces in both aspects of Adam's life: Reki being the obstacle between Adam and Langa (he's literally called "the third wheel"), and Kiriko's investigation threatening his political career.
Similarly, Reki and Kiriko also affected the plot and the main cast on a massive, big-picture level as much as the main villain Adam does: Reki through his friendship with Langa, his ideals that skating should be only done for fun and using the weather to defeat the infallible Adam in episode 11, therefore making Cherry, Joe and the rest of S laugh and see the human side of Adam. On the other hand, Kiriko and the police almost busted S, Adam's fruit and labour, in episode 5, cutting short Adam's race with Langa and making everyone scatter and escape.
It seems as if it was divine intervention that the redheads in this universe would defeat that blue-haired creep.
Unfortunately, Reki's purpose has been fulfilled (by episode 11 and 12 of Sk8 the Infinity) but Kiriko has not.
She's important enough to have a unique hair colour akin to the main 8 cast and be featured in the opening song (and the only female character at that). The OVA has shown us that characters of lesser significance are mentioned/do return back to the show (Koyomi playing a bigger role, Miya remembering Takashi, Reki's childhood friend in Kaoru & Kojiro's flashback), so I refuse to believe this is the end of Kiriko's story.
However, her story can only continue if Kiriko rejects going to Tokyo and stay in Okinawa. It would demonstrate that she was obsessed with catching Adam even if that meant breaking the rules and risking her job.
There needs to be a strong enough motive on Kiriko's part on why she continues to pursue Adam, and I do hope her true motivations will be revealed in time, especially when she's not even a skater in the show about skaters.
This is the part where my speculations come in in trying to figure out Kiriko's motivations. As I've pointed out before, I've seen posts theorising on the possibility of Reki and Kiriko being related to each other, but I would like to propose a different theory.
As it turns out, there aren't just two redheads in Sk8 the Infinity, because one of Kaoru and Kojiro's skating friends as teenagers has red hair.
Canonically speaking, nobody knew what the fuck happened to him or the rest of the DK trio's og skating clique, but what's being a Sk8 fan if not to make some headcanons?
@/painfullyideal proposed that he is Reki's older brother, but I would like to suggest that... beanie redhead guy is Kiriko's older brother.
This tracks with the trend with all of Sk8's supporting ensemble which can be divided into 2 categories:
Are/Were involved in the skating scene in the past or present (Oka, Takashi, Reki's childhood friend, the girl who almost scouted Langa in episode 2 and later Reki had a short-lived crush on in episode 6, all the S background skaters and fans)
Directly/biologically related to skaters (Nanako, Masae, Reki's twin sisters, Miya's parents, Adam's abusive family, ***possibly Kiriko if we go by my headcanon***)
Given that beanie guy is part of Kaoru and Kojiro's clique, he's likely the same age as them, while Kiriko looked more like the same age as Shadow or slightly younger. And if something truly serious had happened to him, she would no doubt try to find whoever did that to her brother, given her sense of justice.
(Beanie redhead guy doesn't have to die, as I don't think Adam in canon is willing to dirty his own hands to the point of killing someone, but something like putting him in a coma or permanently disabling him which could be excused away as a serious skating accident to teach a cautionary lesson could definitely set an angry fire inside someone like Kiriko. She will learn that someone had been sending numerous skaters to the hospital and keep that rage inside of her as she eventually grew up and studied and worked hard to enter the criminal justice field.)
All redheads were destined to defeat Adam, and Kiriko intends to avenge that and set the record straight.
Something else I would like to add anecdotally, the surnames Kamata and Kyan share the initial 'K'; and Kiriko, Kaoru and Kojiro are given names with the same initial 'K' too (at least in English, I know this isn't the case in Japanese kanji).
Regardless, what are the odds of Kiriko being affected by Adam in the same timeframe of Kaoru and Kojiro becoming friends with Adam when they were teens?
Part 3: Is pink a shade of red?
After reading @/dixionduckling's post on Cherry's pink hair could possibly be red but look pink under sunlight if he exists in real life, I feel compelled to explore Cherry's role as Adam's """antagonist""" and the key to what sets him and Joe apart and why he couldn't defeat Adam in the end lies right in front of us from the very start: his pink hair.
As I've mentioned above, Cherry and Joe were Adam's old friends, and so the way they were antagonised against Adam is different from Reki and Kiriko and hinges on their teenage past.
When the "Wedding Beef" tournament started, both of them wanted to race against Adam, but it was Cherry who held the bigger grudge and couldn't let go of the idea of a talented, carefree, mysterious, charming and maskless Adam while Joe had likely moved on (Joe still mourns for the loss of friendship, but he doesn't fixate on the past like Cherry does and wants to give Adam a good punch to the face).
Chronologically speaking, Cherry was introduced to the audience much earlier in the first episode than Joe. Cherry also sets more things in motion for the story's plot compared to Joe, like noticing Langa's potential, getting him to skate against Shadow (which gained Adam's attention), and giving a demonstration of how the Love Hug works. (Don't get me started on the calligraphy scene which isn't only great insight into Cherry's thoughts and feelings, but also great foreshadowing of Adam's ending in the finale.)
Despite Reki and Cherry sharing similarities being two of the smartest and most knowledgeable about skating in the cast (especially in the technical department), I think he's more akin to Langa in this regard, obsessed with chasing their perceived idea of Adam (Langa with 'the zone', Cherry with teenage old friend Adam).
Does this ring a bell with Kamata "I will bring Shindo to court no matter what it takes" Kiriko?
It was because of this shared past that Cherry & Joe were willing to look the other way, especially Cherry, and it was also because of that past that the image of the three of them together got shattered when Adam hit Cherry's face with his skateboard.
No matter what angle you look at, Cherry was never destined to defeat Adam (for now), because his hair is pink.
Even if Kaoru is really a redhead and his hair looks pink under the sun, who's the sun in this situation? Kojiro. And Cherry losing to Adam kinda proves Kojiro's stance with the whole Adam situation right (his "I knew it and I told you so" expression in contrast to everyone else flinching and looking away when Adam smacked Cherry with his skateboard in the face.)
In the end, it had to be our redhead protagonist Reki to defeat Adam first (by showing his fallible and human side) and then Langa to win the tournament and make Adam drop the mask.
Things could still change if Cherry has the chance to race against Adam a second time, to prove that he's our honorary redhead in this universe. His potential relation with redhead beanie guy from the og skating clique, underrated dynamic with Reki, and hopefully a future interaction with Kiriko, leaves a lot to be desired for and look forward to in the next season.
Reki did lose to Adam once very badly in episode 4, so maybe it was destined for Kiriko and Cherry to face a trial of fire and lose before fulfilling their purpose of defeating Adam. I'm finally seeing a trend here.
Part 4: What about the orange-head?
Time's up for headcanons. By now, I have repeatedly emphasised my thesis that the redheads are destined to defeat Adam in this show. Still, I have to address the big elephant in the room: what about my underrated florist clown king Higa Hiromi/Shadow?
He has orange hair so he's a certified ginger, for sure. He's the character in the main 8 cast that frustrates me the most because Shadow could have been one of the most interesting people to contrast and antagonise Adam yet his development and potential is the least explored by the series. The hints are there.
Shadow was the one who researched and warned Reki in episode 4 about Adam's reputation of being dangerous, crushing his favourite skaters one after another and putting them in the hospital. When Miya mentioned that Shadow does the same, Shadow rebuts to not "group me in with the same guy". Even a flashy and violent skater like Shadow whose main method is throwing party bombs and blinding his opponent with laser lights finds Adam's dangerous streak off-putting.
(This reminds me of Joe once saying he doesn't like the way Adam is now while watching Cherry and Adam's race. I would love to elaborate more on how Kojiro is Adam's opposite which I briefly touched on in this post, but I'm leaving it for another time.)
What's more, the fact is we almost got a Shadow vs. Adam showdown if he weren't beaten up by an attacker while protecting his manager.
It was like the showrunners were holding off this particular match for a reason. All redheads were destined to defeat Adam, what if this is Shadow's ultimate purpose too?
Speaking of Shadow's manager, remember that I've categorised the Sk8 supporting cast into two groups? Turns out, the one character whom I haven't mentioned yet, the only other character important to Shadow's personal storyline, is one of two big exceptions to this set of rules I've made (the other being Kiriko).
Flower shop manager is completely unaware of Hiromi's skating hobby or his alter ego Shadow. Her sole tie to the skating show is Shadow's crush on her, but I don't think her relevance would last that long since the show kinda confirms she already has a boyfriend in the finale's mid-credit sequence.
However, we don't know when exactly this happens and Shadow could still hold onto his crush for a while after he finds out. If the OVA was anything to discern, I think this manager crush plotline would be eventually settled once and for all.
By then, I do hope by hook or by crook that Shadow plays a bigger role in the overall narrative of the 2nd season, perhaps move on and find a different purpose to continue skating and becoming stronger. After he passes his trial of fire aka his flower shop manager crush, he would be well on his way to fulfill his purpose as a redhead to defeat Adam, and I can't wait to see the payoff.
Part 5: The falling piece/Conclusion
As much as I hate to say it, but Sk8 the Infinity is arguably Shindo Ainosuke/Adam's show. I guess it makes sense since he's a pretty fantastic villain for a skating show. He's the reason S exists in the first place, and the rest of the main cast wouldn't even know each other if it weren't for S, or specifically each of their unique relation to Adam. No better way to bond than when you've a common enemy, you know.
There's still a number of unresolved plot threads that Sk8 Season 2 could still explore, like the police plotline, Kaoru & Kojiro's past with Adam and their teenage friend group, just Shadow in general... And Adam is really at the centre of it all. His backstory may be explained to us the audience, but a lot of details are still left to speculation.
To the answer the question of why there are so many goddamn gingers in this skating show, I'm gonna end this long theory post with a comment by director Utsumi from this source post: "[Adam's] a guy who stole a main character's color." That colour is undoubtedly red, the colour of blood and passion, and that's why Reki and all the redheads in this universe are destined to take him down a peg over and over again.
