I finally had this epiphany over certain anime I watched before when thinking about moe at all. After some time spent at the website Moegirl and researching what became of the moe phenomenon, I’ve come to realise that Kazuya Minekura’s Saiyuki’s a moe version of the Chinese classic Monkey King./Journey to the West.
I watched it before and while there’s no doubt that Minekura took a lot of liberties with the source material, I think from my own experience indulging in ‘moe’ stuff (like giving characters animal ears) it really is a moe version of that story. Especially with Tripitaka/Genjo Sanzo, Monkey King/Son Goku and Pigsy/Cho Hakkai.
To better understand why Saiyuki’s moe, let’s take context into consideration. Moe, as it came to be, is used to refer to a burning or passionate if sometimes sexual feelings to fictional characters. Saiyuki was actually published as early as 1992, shortly after Sailor Moon got adapted from comics. In that same year, there were a plethora of what some folks call KASG (Kawaii Anime Schoolgirl) games like Classmate.
That too got predated by actual pornographic games, which included stuff as published by Enix. Since these were prevalent before in the 1980s, along with more and more people sexualising anime characters like Fujiko Mine and Clarisse (as well as lolicon) it would be parsimonious to suggest that Cammy, Morrigan, Felicia and Chun Li are also KASGs.
Not to mention it also coincided with a growing fan sexualisation of franchises like Captain Tsubasa, Jojo’s Bizarre Adventures (the Clamp girls did it with not only introducing a fanfiction between Kakyoin and Jotaro but also made characters inspired by them in Wish), Gundam and the like.
Whether or not Minekura was influenced by those franchises’ up to anybody’s guess but given these predated Saiyuki it would’ve been unconscious. Nobody knows how and when moe came to refer to such feelings for characters but it could’ve been popularised by Sailor Moon (Hotaru Tomoe, though she’s often referred to by her first name), Dinosaur Planet and others.
Then came Evangelion which according to some like Azuma Hiroki further cemented this. But in the sense that characters can be easily made interchangeable with one character with regards to the fans’ desires. Ayanami Rei’s retiring nature and odd hair colour’s made interchangeable with others like RahXephon’s Quon Kisaragi and Haruhi Suzumiya’s Yuki Nagato.
So much so you can make a database out of desirable traits and characters. (There’s already a website like this.)
Let’s not forget that Saiyuki’s very much a product of its time in a way, especially when moe got popularised in the 1990s. It boils down to the way the characters’ portrayed. Sanzo’s a tsundere whilst Hakkai and Goku are yanderes. Tsunderes are those that seem aggressive, brash and offputting but deep down inside seriously want intimacy and affection.
Yanderes are the opposite, seemingly affectionate but secretly or become murderous and savage. In the original story, Sanzo’s just a monk (well a more stereotypical one at that, pious and calm), Hakkai’s a pig and Goku’s an actual monkey. Like I said, Saiyuki’s a moe version of the Monkey King.
For Sanzo, it’s got to do with somebody so pious to the point of becoming preachy, off-putting and belligerent to nonbelievers but deep down inside secretly craves sinful and worldly pleasures. It’s not so much in how Sanzo’s actually portrayed but rather the idea of making him a tsundere fits into this.
(Amusingly enough since TV Tokyo aired both Saiyuki and Evangelion, Asuka’s father’s played by Sanzo’s voiceover artist Seki Toshihiko. He didn’t just play a tsundere’s father but also played a tsundere himself. Like father, like daughter.)
As for Hakkai and Goku, as far as pet pigs and monkeys go, they’re both intelligent animals that can be owned and tamed/domesticated (especially in Southeast Asia with regards to monkeys being made to get coconuts) but from my personal experience owning pets, though appealing they can become really irritating.
That too isn’t always the case but given my habit of drawing animal-eared characters from researching on such beings it’s close to how Minekura would’ve interpreted them as. As for Sha Goijyo being a kappa (or water monster), it’s more to do with that since a water monster could easily kidnap a person, it’s not hard to imagine it seducing it as well though creating a bloodbath also counts (it plays into the anime cliche of horny nosebleeds).
Saiyuki only seems loosely based on the source material if you take away the moe glasses. With the moe glasses on, you tend to reinterpret things differently in accordance with your preferences and desires to the point of sexualising them (at times).