Round three, to tie this mess I've created. This's going to be so wild since almost everyone mentioned here are all missing cannon to load to a ageless ship.
Meet the DDC
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Here comes the Tsunami
Wakasagihime: She does not have a canon age. (running a bit out of canon jokes). The first recorded mermaid sightings in Japan are found in the Nihon Shoki one of the oldest books of classical Japanese history, dating back to 619 CE. If we're using that she's already 1403 years old. (I want to bring up the tale of Yao Bikuni but the moment is not right as of now)
Sekibanki: She should've bought a canon scarf to hold her head and to blend in with the villagers. 2 in one: rokurokubi and nukekubi which is from edo. (1600-1868) Guess what she's going to join the couple hundreds year group.
Kagerou: Why? Their species are now canonically gone extinct in 1732 which is once again Edo period. The last specimen was officially killed in 1905 in Nara Prefecture on Honshu Island, Japan. So, I'll assume she is alive and well before 1732, making her over 290-422 years old.
Seija: I have no idea about this one I mean she flipped nonac. Wild guess, but most likely centuries old but younger than an oni. Your average oni has a life span of six japanese eras. 2000 might be acceptable.
Sukuna: It is said that an inchling was part of creating the Japanese Islands along with Ōnamuji. Yeah, she is missing out a canon needle. She maybe a millennium or a house wife years old.
Raiko: If we're counting the old canon drum, she'd be crossing the centuries or half of century and would become as old as Patchouli. If not, I don't either, What if that doesn't count? Well, give her the decade pass.
Benben and Yatsuhashi: New yokais at the time of DDC and Ben 10 is older than Yuto Yatasuhashi although they aren't blood related just became sentient at the same time. Same signature as Raiko decade or 5 decade. Your move.
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LoL LoLK LoL
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Someone shoot down the suns and the canonballs are lost in the process.
Seiren & Ringo: If we're talking about war, there're two of 'em: Genso-Lunar War which was one thousand years ago and Lunar War which I think is only a few decades ago. I'll bet on the second war making them as old as Reisen or perhaps younger. Those two I think roughly have 2-4 age gap.
Doremy not so sweet: She is a baka baku whom originates in Chinese folklore and was familiar in Japan as early as the Muromachi period (14th-15th century). If I have take this as reference, she would be over 600.
Sagume: She may be based in part on Ame-no-Sagume, an earthly Shinto goddess that “instigated” heavenly messenger Ame-no-Wakahiko into rebelling. Did I go too deep eh? She would be on par with Suwako and Eirin.
Clownpiece: A hell fairy and a lampad? Take this century pass and welcome to the playground of "Canonball Carnival". (Don't forget fairy are also as old as the nature)
Junko: How many sources have I searched upon? Hou Yi became the leader of the Xia Dynasty, he later caused the death of her son, Bó Fēng meaning Junko was alive during the Xia Dynasty and possibly before. Finally, the prediction will be accurate once more since the Xia Dynasty was 2070-1600 BCE thus, making her 4000 years old mama.
Hectia: Based on a greek figure, Now back to Hou Yi (also known as Shen Y), he shot down the Nine Sunbirds. Because of this occurrence, Apollo was shot down, darkening the hells Hecatia was overseeing. This points to one thing, she was alive during the Xia Dynasty and even before like Junko making her over 4000 years old.
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HSiFS the no canon age for you
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My tooth hurt when writing this.
Eternity Larva: No canon cold for you. My Okina speculation suggests that Eternity may have been inspired by the story of the Tokoyo god. If you this according to Nihon Shoki (The Chronicles of Japan) she would be set in the 7th century making her the same caliber as our contestants above.
Nemuno: A yamanaba, now this might be cannoning, I'll put her in the centuries group.
Aunn: Statue of guardian dog: Goryeo (an ancient Korean dynasty). So, you want to go back a millennium to the past?
Narumi: She is based on the hatted Jizo statue, too many number to count from. If we're talking about her recently after the incident, she decades old.
Mai and Satono: Okina does replace the old dancers with the new one every once in a while. Decades or centuries?
Okina: Older than Gensokyo itself and so she joins with Yukari.
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Manga Characters
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I'm getting more tired.
The Three faries: Lunar, Sunny, Star: I give them the verdict of being younger than Cirno.
Reisen 2: Younger than the moon rabbits in my eyes.
Rinnosuke: Un-known but he's a few decades old.
Watatsukis: Toyo & Yoro: Both of them are at least 1500 years old.
Kasen: Joins Okina and Yukari for smash. Yeah, older than Gensokyo.
Kosuzu: Younger than Marisa/Reimu/Akkyu. She might be starting her adulthood soon ~17-19.
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CD Characters that found the cannon fuse
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Whew, no more cannon balls for now.
Maribel: around Sanae age.
Renko: Yeah, her too.
Akyuu: 27 right now. (stated by Von above) 1,200 with past lives included.
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Spinoff Characters likes to spin with Hina
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Five waves of storms flushing out the cannonball.
Iku: The messenger herself (Oarfish). She's missing a canon report to the Dragon Palace. Tons of thousands of years old maybe over than that.
Tenshi: Aren't Celestials supposed to have a very very long life span. I've lost the canon count right of now. 5-7 digits, give or take.
Hatate: I'll place my bet, she's younger than Aya.
Yorigami sisters: Joon & Shinon: If we track down the gods, they might be around at the start of the canon land. 4 damm digits or even higher. Joon is younger than Shinon of course.
Suika: let's put her right next to Yuugi and make her a bit older maybe?
KoKoro: I've been losing the cannonballs a lot. Wait, she has one and it's called over 1300 years old.
Sumireko: She's 15-16 as of Urban Legend in Limbo. She is most likely in 19-20 right now.
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Dispencer down!! Pardner, Gou don't think it can go on any longer for tonight, after looking back and forth from the wikis.
I promised ya: I'll covered the last two games including one of my favourite "yuuma toutetsu". For now I'm out of breath and going have a long comfortable sleep. Don't mind me, the enginner is the enginsleeper.