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shimizua then, how you explaine "moon" element, mentioned in the same chapter later? )
Sorry for necroposting, but this might help others, so I'm gonna just write it down here:
The Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn correspond to the seven days of the week, starting from Sunday. It's fitting, considering how the 12 Stars of Heaven are named after the western astrological zodiac signs/constellations.
However, in Japanese culture (and probably other Asian cultures),
Tuesday to Saturday correspond to the eastern Five Phases/Elements. That is to say, they correspond to 金、木、水、火、土 (Metal, Wood, Water, Fire and Earth). Sunday and Monday correspond to Yin (Monday) and Yang (Sunday), the two poles/dualities in Daoism and which permeate most of eastern culture. Normally, these seven are grouped together as Yin-Yang and the Five Phases/Elements (and in many cases, each of the Five Phases/Elements has a Yin and Yang variant).
And yes, East Asians also use the
Eight Trigrams, also from Daoism (search up the I Ching for more info if you need), which are symbols representing eight mutually opposing and reinforcing facets embodied in nature. Each trigram corresponds to one of the Five Elements (which does mean some elements are linked with two or more trigrams).
The trigram 巽 (the Gentle) whose image in nature is 风 (wind) is connected to the Wood Element.
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Yeah, it's quite a bit to take in, and since manga (alongside many eastern light novels) is catered to East Asians (go figure), many manga often assume you have some level of understanding of
The Five Elements, Yin-Yang and the Eight Trigrams. It also does mean that it becomes a royal pain when some pieces of media starting going deep into the Daoist cosmology and methods, since very few just explain it. It's like how many pieces of western media assume the existence of the Four Elements, or take the foundations of Christian cosmology for granted when expanding upon it.