PC-98
The Shrine Maiden Reimu Hakurei is able to frantically persuade a bouncing Yin-Yang orb to hit various on-screen targets, "cards" and "bosses" alike. The Yin-Yang Orb is her only true weapon against the powerful enemies, but she lacks the training to be able to fully control it. As such, she must avoid contact with it at all times; should the orb impact Reimu, she will be hit, and a life will be lost. However, Reimu can knock and manoeuvre the Yin-Yang Orb around by whacking it with her gohei, slide-tackling it or firing an ofuda at it. Only the Yin-Yang orb can damage the enemies, so simply firing your shots at enemies will have no effect.
When the orb passes over a card in the field, the card is considered to be hit (though no actual collision occurs). In most cases, a single hit is enough to overturn a card and eliminate it from the field, though in later stages, occasional cards will require multiple hits to overturn. Additionally, when the orb impacts a boss's weak point, the boss takes damage and loses a single notch from its health bar. Furthermore, the orb can dispel small white bullets (but nothing greater) as it passes through them.
In the endings to Highly Responsive to Prayers, the Orb appears to transform into either a tiny wish-granting fairy or a joyful spherical creature. In Makai route good ending, Reimu thought the tiny fairy can grant wishes, so Reimu wished for money, a cake, a hot meal, "the truth of the Universe", and the "destruction of Earth", with a response from the fairy: "Who'd wish something like that!?" In the Hell route good ending, the joyful creature starts destroying parts of the Hakurei Shrine and Reimu gets angry.
Depending on which ending you get Genjii will explain the orb's "true power", each of which is hilariously mundane and is never spoken of again in the series:
- The ability to eat sweets and not get fat
- The effect of giving its user whatever scent they desire
- The ability to turn into a cat whenever the user chooses
In Phantasmagoria of Dim.Dream, the orbs were for the first time treated as ordinary projectiles, used on the opponent's screen whenever Reimu summons an attack. If Reimu were to summon a Boss Attack, then unlike other characters who use their own body to be on the opponent's screen, the appearance of a giant Yin-Yang appears instead.
Also used by Reimu when she's a playable character, the Yin-Yangs appear as ordinary danmaku on Stage 4, supporting Reimu during her boss fight as they bounce downwards towards Marisa.
Windows
Also used by Reimu when she's a playable character, the Yin-Yangs appear as a generic enemy on Stage 4 just like they did on Lotus Land Story, supporting Reimu during her boss fight as they bounce downwards towards the heroine; because they're destroyable, it wouldn't be best to treat them as danmaku. The orbs can also throw danmaku. However, similar to other spirits throughout the game, if the player chooses to focus, then they'll become transparent, undefeatable, but also harmless, which simplifies gameplay.
In Phantasmagoria of Flower View, the Yin-Yangs weren't shown to be a default weapon for Reimu Hakurei, but instead they appear as Reimu's Extra Attack. If Reimu were to kill a spirit, then a black and white yin-yang will appear in the opponent's screen and bounce downwards from the top, being ordinary danmaku. However, they've doubled in size compared to their previous game's counterpart. If the player is using the alternative version of Reimu who uses a blue outfit, then her Yin-Yang Orbs will be aqua coloured.
In Subterranean Animism, Yukari modified the Yin-Yang Orb to act as a communicator to stay in touch with the other youkai while Reimu went to Former Hell.
In Unconnected Marketeers, Misumaru reveals in Stage Four of Reimu's scenario that she was the original creator of the Yin-Yang Orbs, having made them out of similar materials to the dragon gems, and her spell cards include the use of multicolored Yin-Yang Orbs.
