Otoya Kurogane

Otoya Kurogane is the heir to the Kurogane household, a powerful crime syndicate with strong ties all around Japan. Despite Otoya's desire to live a honest life as a veterinarian, the young man was constantly groomed to assume control over the group once his mother passes away. Fleeing from a life he didn't want to live, Otoya eventually arrived in Ikeda. While there, Kurogane, studying to reach his dream, discovered that he possessed unusual abilities. Especially centered around the strange oversized calculator he had been given by his mother many years back when he was required to function as an accountant (keikai) for the family.

As luck would have it however, he wasn't the only one who noticed. A member of the organization known as Xstence eventually contacted him and taught him about the origins of his powers, the existence of Shinigami and Hollows, and about the organization itself. Wanting to know more about his own abilities as he was, it didn't take much convincing. Surprisingly, he revealed that he had encountered Hollows several times during his life, but had written them off as merely being rivalling families attempting to give him a fright, it wasn't until they informed of the grave threat they posed that the young yakuza heir realized just how lucky he'd' been.

Evidently, his mother, Kumogi Kurogane was attacked by a fairly small Hollow while he was still in her womb. But like her son, she mistook it for an agent of one of their rivals, sent to frighten her and make her back down on securing their current territory. Enraged, she'd stabbed it in the eye with her dagger, which just so happened to be a dagger used in rituals to banish foreign spirits. It's been suggested more than once that most of the Kurogane syndicates wealth stems from pure luck, and with such an incident, that might very well be the case.

Fullbring
Nasty Accountant (ナースティー・アカウンタント, "nāsutī akauntanto"): Otoya's is focused through his calculator, an unusually large object with a design of green and black. Unlike many other Fullbring, Nasty Account is centered primarily on support, which it accomplishes by keeping track of and incurring debt on an enemy. Whenever an enemy attacks, uses a technique or ability within approximately two hundred meters of Otoya, the calculator immediately calculates the approximate power and intensity of the attack and assigns it a price tag. Should the intended victim (typically one of Otoya's allies or Otoya himself) evade this attack, this calculated number is immediately incurred as a debt towards that subject - visible as flickering numbers of green light above the person whom that enemy is indebted to. These aren't invisible by any means, and can be seen by anyone with spiritual awareness. For as long as the enemy is indebted to one of his allies, any connecting attacks from that enemy will reduce their debt as opposed to damaging the target in question. Notably, it's possible for multiple opponents to assist in paying back a targets debt, but this is risky, because multiple missed attacks at once typically causes the debt to skyrocket.

According to an explanation given by Otoya to his team, the Nasty Accountant requires at least two people to be an effective tool in combat - as it's major flaw is that Otoya's own attacks are effectively neutralized, with any attacks he connects instead being added to his opponent debt rather than damaging them. Otoya is classified as the Accountant, whereas he can assign up to three collectors. The collectors are afforded the protective powers of the Nasty Accountant, but still remain capable of attacking and damaging their enemy - the role of collector is typically inferred on the most offensively powerful members of Xstence.

Clever use of Nasty Accountant in combat allows Otoya and Xstence as a whole to combat extremely powerful opponents, because such beings often incur an extremely high debt for each missed attack. That debt can further be turned into a weapon with some of the Nasty Accountants other abilities.
 * Price Level & Bankruptcy: In much the same manner as Nasty Accountant can readily calculate the strength and power of an attack, it can likewise provide an approximate calculation on the power of other beings. This is referred to as their Price Level, and it represents their level of skill and ability, although it doesn't always denote their skill in fighting, it's usually the case that a being with a higher PL has more overall power than one with a lower one. As Fullbringers, most supernatural creatures above the level of a Lieutenant vastly outclasses them in direct combat, especially Arrancar. Although the Price Level might seem a pointless tidbit of knowledge, it does has a true purpose in judging both themselves, their opposition and even aids in formulating strategies. As when an enemy incurrs a debt that exceeds their Price Level, the result is an immense reduction in all physical and spiritual attributes, which Kurogane has calculated at being roughly a reduction of seventy-five percent. After this event, their debt resets and the entire cycle repeats additively each time they accrue more than their current Price Level, with each breach weakening them further and further until they're eventually on the level of ordinary humans.
 * Nasty Credit: When Otoya and his allies finds themselves facing extremely dangerous foes, it's often necessary to give them credit in order to give them a fighting chance. For Otoya to give himself or any of the collectors credit, there's several conditions he must fulfill. Firstly, he must know the name of their enemy, and secondly he must not have used it before in that fight. When used, it immediately gives the targeted enemy a debt against up to four people, comprised of Otoya himself and the three possible collectors. The amount of credit given depends upon Otoya himself, but it's typically a fairly high number. But such a powerful ability doesn't come without it's drawbacks, as each affected person has roughly two minutes to pay back their debt against their enemy in damage. If this fails, the amount that's left unpaid is immediately taken from their own energies - which can lead to Bankruptcy.