Circumzenithal Arc (a Touhou LW original) refers to a rainbow-like arc that forms in the sky above the sun when ice crystals refract incoming sunlight. This is an apt temperament for this Kasen, who continues to journey across parallel worlds, searching for the cause of the incident. There are two Kasens One is a hermit and is alive today, and the other is in the past. The hermit Ibarakasen is making an effort to accept her past self while distancing herself from them entirely. The two have much in common (Metal Phase) but also function as opposite sides of the same coin (Moon Essence). The cold and silent Metal Phase resists Earth Phase, because earth bears metal, but it is weak to Fire Phase, because fire refines metal. The cooperative and indecisive Moon Essence resists the alluring and arrogant Sun Essence, but it is weak to the diverse and uncooperative Star Essence.

The ability of Kasen Ibaraki, who has almost reached the end (a Touhou LW original). Kasen 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. Even as a hermit, Kasen Ibaraki had limited options to combat the big incident. She had banned herself from using her true power, but even if she hadn't, using it would have caused such havoc that it simply wasn't an option. She had once managed to trick her arm into being resealed, but that wouldn't have worked a second time. No matter how bad things got, using her true power was strictly impossible. The following assumes that Kasen Ibaraki was once an oni. Kasen searched far and wide for her arm in the hope of resealing it. With some assistance from the Hakurei shrine maiden, she enacted an elaborate yet bold plan, which led to an ultimate showdown between Kasen and her arm. The two can no longer become one. And so Kasen can never again use her true power. The phantom pain she feels where her arm used to be, the sealing curse that was placed not on her arm but on the wound it left behind, and the flesh torn open by Onikirimaru's slice will never let Kasen be at peace. Kasen's oni arm wishes to rejoin its former body, but the wound created by Onikirimaru the Bewitched Blade, won't allow it. If the pair ever rejoined, then Kasen Ibaraki may transform into a terror that brings this world to ruin. "OK, here's what we'll do..." It was a plan you wouldn't believe came from a hermit. After all, hermits are supposed to be noble and kind. But to all who knew her well, it wasn't all that unexpected. The idea was to coerce Kasen's arm into rejoining her body and get it to use a level of power essentially equal to Kasen's true power. Then, they'd have the curse on the wound left by Onikirimaru thwart the arm's attempts at rejoining. The pain from the curse would be nullified with the power of the Ibaraki Box of a Hundred Medicines, which would finally allow Kasen to use its healing properties for herself. ...And if all of that succeeded, they'd be able to use the arm's power without having it rejoin with Kasen. What was once Onikirimaru the Bewitched Blade is now Onikirimaru the Phantom-Limb Blade. Kasen found one fragment of the shattered blade, but there were more. With youkai energy binding them and memories of the past to guide them, they returned to their original shape. This, in turn, seems to have recreated the will of the blade's former master―the very samurai who sliced off Ibaraki-Douji's arm...