Shadow Spear: Surrounds body in shadow that forms into a spear.

Ability to see through shadows, also allowing him to see in the dark.

Chokusetsudensen - Direct Infection - A
After capturing a soul in correlation to Specific Soul Control (meaning through killing a character), Yui can sacrifice pieces of the soul in order to convert the soul into an infection that can be compared to a venom. The more of a soul she sacrifices, the stronger the infection. When sacrificing the soul, she loses a portion of the abilities she could have gained; however, since this conversion can be done at any time, Yui can wait to sacrifice the techniques she gained from Specific Soul Control.
This infection cannot truly be called a venom, because it affects the soul, and souls don't have a blood stream; however, it works similarly.
Again, the more of a soul Yui sacrifices (i.e. the more jutsu points she gives up), the stronger the infection. Furthermore, the infection is progressive. The higher the the amount of jutsu points sacrificed, the greater the final effect. In higher infections, it touches infections one and four. Meaning, any infection above one starts off at one, then advances to whatever its final infection is. Any infection above four, starts off at one, then goes to four, then finally takes affect. (e.g. If infection 8 is used, the target will first experience infection one. Once it is over, they will experience infection four. Then, finally, infection eight)
1: A minor paralysis of the soul occurs, continuously blocking out a single technique each post in the order they're listed (although Yui gets to decide where it starts). Only one technique is blocked per post, meaning any previously blocked techniques are usable again in the following post. The length this lasts depends on the amount of techniques someone has, because it only stops after it infects every, single technique.
2: Same thing as sacrificing one jutsu point, except it goes through the target's techniques twice.
3: Same thing as sacrificing one jutsu point; however, the length of posts a technique is blocked increases to three posts. Unlike the first one though, it only infects a quarter of the techniques (rounded down, if necessary).
4. A new type of paralysis that infects the soul's ability to manipulate the target's body, or any other object, for that matter. The two have separate results though. When it comes to someone's body, their limbs are temporarily sacrificed, one post for each leg, two for arms. And finally, it causes a full-body paralysis for a single post. When it comes to objects, the distance at which they're manipulable alters (this really only affects Chiyura -- or someone with the ability to manipulate their soul). During the first one, their ability is cut by 80%. Second: 65% Third: 40% Fourth: 15%
5. By sacrificing five jutsu points, an infected person loses all of their techniques temporarily, regaining one each post.
6: By sacrificing six jutsu points, an infected person essentially loses 75% of their soul, allowing Yui to temporarily capture the soul and use 6 of the target's jutsu points, which consume none of Yui's chakra. With only 25% of their soul, the person loses consciousness until the soul is returned; however, the infection temporarily affects that 25%, creating an impenetrable barrier, preventing the person from being reached, which also prevents them from being attacked. The infection only lasts 4 posts; however, when the person gains consciousness, they're chakra supply is cut by half.
8: The strongest infection. Essentially the very first infection, but permanent, and a bit stronger. A technique is sealed for two posts, and it infects the entirety of someone's techniques in the order they are listed; however, Yui does not get to choose where they start.
Finally, how does one become infected? The result may vary. The infected soul can be sealed into a piece of equipment, and depending on what the equipment does, how the infection occurs may change. A bladed weapon would require you to cut someone. A blunt weapon would require you to hit someone. A shield would require you to block someone's physical attack.
Another way to infect someone is through simply manipulating the soul via Mass Soul Control; however, since this version is only visible to those who can see souls (not even every Chiyura can do so), there are some limits on it. If this method is chosen, the infection is practically impossible to avoid; however, it takes two posts to accomplish. During these two posts, Yui may not move her body, and the only abilities allowed are those solely related to her Mass Soul Control.
After an infection occurs, the converted soul is destroyed.