Starry Mountain of Tenma
Touhou astrology overalls
This article will focus on the basis for analysing all of the charts of the games, see what they all have in common, tenedencies, etc. The first obvious common thing, is that all the mainline Touhou games, with the only exceptions of Touhou 3 and 5, have Sun in Leo, as they were all made in August. This is a very important factor as ZUN himself has Saturn, of all planets in Leo. Saturn rules the weighted part of one's life "the oppositor". On Leo, this is applied to creativity and individuality. It normally manifests as someone wanting to be something great, wanting to manifest themselves artistically in a big way.
The weight also blocks overall creativity as natives with Saturn in Leo focus too much on "doing something great", but as time passes on, through relentless testing on that area, Saturn will slowly and slowly get weaker/more benefic for the person born with it, this applies to all Saturns. Saturn in Leo is no different in this regard, With ZUN also having his own noticeable creative journey with the games.
Every mainline game the Sun was conjuncting the position of ZUN's Saturn, astrologically, this brings consciousness (Sun) towards the obstacles and limits (Saturn). This implies that every Touhou game made by ZUN was a battle against his own limits creatively, the bringing of light and consciousness towards what he was capable of creating. The peaking of this, was at his Saturn return, which happened during Touhou 10. To further understand Zun's creation, let's look at the birthchart of not only Touhou 1, but also the series itself.
First thing that calls attention is the charatecterizing Sun in Leo' 22 which will repeat itself a lot. You also see that Saturn of this chart trines ZUN's Saturn. A trine means an expansion in the area that it represents, Zun had Saturn trine his Saturn and thus expanded his creative work into Touhou. Pluto also was entering Sagittarius (the "religion" sign) right as he created it, which can serve as pre-text for the eventual revival of native gods that Touhou found itself domino-ing into. The south node finds itself in Aries, conjuncting Saturn also in Aries, while north node is at Libra 12th house. This could represent the overall turn of the series from a more detail-focused work to something more whole and transcendental with a whole world built around it.
Also, it's poetic to think of how South node, where something comes from, is in Aries(conflict, intensity) and North node, where it will go, is in Libra (Peacefulness, equilibrium) with Chiron(healing), for when you think about it, every Touhou plot is fighting followed by harmony between the 2hus. Another thing which foreshadows the native gods' intervention is the Neptune and Uranus having the IC on them both, while Neptune is on Capricorn. Although Capricorn is known for it's "materialmaxxed" ways, it's also the sign that rules shamanism equally to cancer, rites which involve contact with loads of yin-entities use the moon in capricorn.
Moon(ruler of MC) finds itself on the tenth, but conjunctin the eleventh cusp, the natural house of spirits, daimons, etc. With Virgo being also a Karmic sign(it opposes Pisces!). Venus was by all means a Morning Star in the creation of Touhou, Conjuncting Mars, thus acting as one with it and even more active than normal. Both find themselves at the sign of Cancer, the maternal sign which's nature inhabits all existence on the instinct of the soul's nutrition. You find them opposing Jupiter, thus also acting as one with Jupiter. All this put together with the third house-ninth house axis, and you see the manifesting of native(4th) forces that influenced Zun on this creation.
Where to look first
After these considerations, one with medium-knowledge of astrology can easily understand any chart of a Touhou release. The order that you should look for things are: First you watch for the Venus' position, as Touhou are always Libra ascendant, Venus rules the game, thus you should look at it first, what sign it's in, what house and see also what's aspecting it, which such a maneuver you can deduce using the archetypes the general nature of the game. By the date of the games together with the fact that Venus can only be 47 degrees maximum from the Sun, Venus options are limited to the 12th, 11th, 10th and ninth house, and the signs of Libra, Virgo, Leo and Cancer.
The second place to look for is the Moon, as the Moon not only is the subconscious image of self and all the other meanings atributted to it, but also, in 2hu's case, always the ruler of the MC. The MC rules not only the "person's career" (this is an oversimplification), it is the Square of the ascendant, therefore tension between the point of the MC and the self (ascendant), which means that the self will be pulled towards "defeating" what the MC represents, and in the end (as all stressful aspects like the square) integrating the meaning of the MC(People get more and more like their MC as they get older too.) in Touhou's context you can see the MC as a main "pointer" to further understand and interconnect your interpretation of the other aspects.
Lastly and third thing you should give a look to, is comparing the chart of the specific Touhou game to the chart of the first one. This will add extra meaning as it will show what the game in specific means to the series as a whole. For example, Touhou 6's chart has Saturn in the first Touhou's eighth. Transit of Saturn through the eighth is not only a time of "purgatory" but also a restructuring of your beliefs, think of the eighth as the 12th house(self undoing) from the ninth(beliefs and "where-to-go". With that you can induce that Saturn was destroying the "where-to-go" and predefined beliefs of the series during Touhou 6's creation, to later (as Saturn transited ninth, During Touhou 7 and 8) create an new meaning again.
Touhou
As a parting note, it's interesting to lastly point how this chart has LOTS of stressful aspects. Stressful aspects in astrology aren't exactly "bad", they are just, well, stressful. They create a tension between 2 aspects, but as time goes on, the tension is integrated, and what was before a dificulty, turns into a talent. A square has the nature of Saturn, representing the number 4 of foundation(360/4 = 90, the square aspect in degrees), 4 in tarot comes right after the first 3 cards of the Magician(creation), the High priestess(duality) and the Empress(the expansion and birth of something out of the dance of the previous duality). But the things that 1, 2 and 3 represent are still "soft", without structure, without tradition which needs for it's development and completeness. And then comes the number 4, representing Saturn, the card of the Emperor. That is the numerology behind the square aspect, and similarly, the opposition and other tension-like aspects.
With this said, you can see lots of those into Touhou's chart, and this is a reflection of the difficulties that ZUN himself had to go through on it's development(as said before, the undoing of the blockings). All those tension aspects, eventually evolved and integrated themselves into beauty and an harmonious connection. One could even say that this is another reflection of the Libra north node that the series has, the creative journey of ZUN himself, from tension to harmony.