Terifuri (a Touhou LW original) refers to an uncertain situation or sky that constantly shifts between rainy and sunny. This is an apt temperament for Yukari, the youkai who created and nurtured Gensokyo and is destined to perish alongside it. Beneath a smaller-than-normal sky (weak to Moon Essence), surrounded by vast, beautiful mountains (weak to Wood Phase), she crawls along the ground (strong against Earth Phase) while her heart and mind take flight (strong against Star Essence).

The ability of Yukari Yakumo, who has almost reached the end (a Touhou LW original). Yukari completely lost this ability due to a Lost Word. She is currently regaining it little by little, though not through restoring or replicating her old ability, but with a newly constructed original ability that formed a core to build upon. She has continued to travel across worlds to try and end the Lost Word Incident. Recreating Gensokyo was impossible. Something was missing. The Lost Word Incident erased something that was absolutely necessary, turning it into the True Lost Word. Yukari Yakumo only learned this fact after she tried to recreate Gensokyo. Knowledge and experience can't just be picked up on a whim. They must be earned through deliberate experiments. Just as abilities must require a cost―otherwise they'd be omnipotent―to gain this knowledge and experience, sacrifices must be made. Yukari spent many resources only to learn that she had failed. Unlike the Great Hakurei Barrier or the Youkai Expansion Project, Yukari's creation of Gensokyo is not a singular historical event. Those events only occurred after Gensokyo had been created. Without a Gensokyo, they're meaningless. You might think that to learn about Gensokyo's creation, you simply have to look even further back in the past, but since this touches upon events not recorded within the true data, you will not find what you seek. So what can you do? You can compare your Gensokyo against other Gensokyos. Not parallel-world Gensokyos, but the Gensokyos living in the imaginations of people in far-off worlds. Yukari's great theory was that by catching glimpses of these imaginary Gensokyos, she could turn them into seeds from which a new Gensokyo would grow. However, when she tested this theory, it failed. After witnessing this experiment, Wordsmith decided to cross over to the next brane. By Wordsmith No. 80 acting as the main booster, and the local Yukari Yakumo acting as the auxiliary booster, she achieved the necessary escape velocity. After fulfilling their purpose, both boosters were discarded as dead weight, breaking down into particles that spread across the entire universe. This was part of Wordsmith's plan since the start. It is known as Fantasy Regression, and has been performed in all the universes before this one. However, it's not like all hope is lost for this universe. Nothing is perfect, nothing is ever certain, and all things require an appropriate cost. This means there is always a chance of making mistakes. Eventually, all things will break down and fail. No matter the journey you're on, you will always lose something, but you should find something, too. It's possible, even likely, that the True Lost Word can be found toward the end of such a journey. If not, there should at least be a clue. So, it might be a good idea to prepare for when that time comes. Perhaps someone will come and deliver it. It's also possible to travel backward along the path already trodden. This is the Fantasy Progression to Wordsmith's Fantasy Regression. It should be much easier than fighting against the current. It's like how rockets need an exorbitant amount of fuel to reach the Moon but don't need much at all to return to Earth. Also, if you continue to hop between worlds, you can wait for someone to deliver what was lost while continuing on your journey. The only problem is that there's no way of knowing who will deliver it to you. The 80th Theoretical Gensokyo This is the egg, the seed that could potentially grow to become the 80th provisional Gensokyo. It exists both within and without Yukari Yakumo. It flows in and out of her. And within this seed lies a single fragment of Wordsmith No. 80, which fulfills the role of its nucleus, DNA, and starting variable. Wordsmith looks up at the stars each night, dreaming of the day when Gensokyo is finally born. Even now, she continues to imagine a flying shrine maiden and an ordinary magician, believing that one day they will become reality.