The Sword of Hisou (緋想の剣, Hisou no Tsurugi, lit. Sword of Scarlet Perceptions) is a celestial relic and one of Tenshi's weapons in Scarlet Weather Rhapsody. It has the ability to exploit an opponent's weakness, no matter the circumstances. First, the sword converts the opponent's spiritual nature into scarlet mist, then into a form that can be seen. Once the opponent's nature has been revealed, the sword can change itself to channel the most effective attributes to counter that nature.
The spiritual nature evoked by the sword takes the form of weather, which is why it somehow looks flexible. Also, spirits slashed by the sword become scarlet mist. This mist can be used to influence and control the weather. The shape-shifting properties of the sword mean that Tenshi can keep it anywhere on her body without taking up space.
Additionally, it can be drawn from seemingly nowhere in battle, and is durable enough to channel the powerful strength of the celestials, allowing Tenshi to rupture the Earth or even cause earthquakes in the surrounding area.
Tenshi can also evoke the gathered scarlet energies of living beings through the sword, creating an immensely destructive beam that inflicts grievous injury upon her opponents.
Other abilites include:
The scarlet energy of the sword can be channeled to provide Tenshi with super-armor for a short amount of time.
Tenshi can imprint the "封印" (romanized: "fuu in", meaning: "seal" or "stamp") of the sword upon an opponent, dealing substantial damage. This seal contains the scarlet energies of the current local weather and will be more or less powerful depending on the type of weather.