The Fusion Technique is a highly forbidden technique, used to fuse two individuals of almost equal power into a single individual with skills and abilities much stronger than the two fusees. It can be performed by anyone who has a zanpakutō spirit and has been trained in the usage of the skill; though only members of the same gender can perform the fusion.
The fusion itself takes quite a lot of time and effort to perform, as both users are required to meditate while facing one another and in direct touch of their partners zanpakutō. Firstly, they adopt a meditative stance similar to Jinzen and lay their hands upon their partners zanpakutō. The process afterwards is what takes longer, as the users must then go to their own Inner World, causing their own zanpakutō spirits to enter another plain of existence; causing both physical bodies to be pulled together and fused. However, the two beings are not equals during this period of meditation; as one is required to lead while the other surrenders. The time required for this portion of the technique varies with the two individual users. It may take minutes for those familiar in the usage, while others could take hours. Complete trust and faith in your partner is also essential, as feelings of doubt and despair will cause the fusion to backfire.
The end result of the fusion are two individuals with greater levels of strength, speed, spiritual energy and intelligence than the original fusees possessed separately. The fused individuals personality and appearance is a blend of both fusees with a part all their own. From the fusion, two individuals can be born; based solely on the roles assigned during the meditation period of the execution. The one leading will gain a higher level of dominance should the fusion be successful; contributing more to the personality, appearance and balance of powers and abilities.
The fused individual possesses a single zanpakutō that takes on aspects of the two fusses; though any transformations, such as the Teni Muhō no Kiwami of the Yakubyougami become unavailable and instead become spiritual energy for the fused individual to make use of. Like a Shinigami's zanpakutō, the weapon possesses a Shikai and Bankai state; though their version is much more potent than that of either fusses' original zanpakutō.
The fusion has some limitations that limit the overall power of the technique:
The first is the potentially long time it requires to initiate the fusion itself; as one would need trusted allies to act as a diversion in order to perform the technique itself.
The second is If the fusion was successful, the state will last only for a period of forty-five minutes; with shorter times depending on the power of the individual fusion, meaning the more powerful the fusion, the less time the user has before they split again.
The third is the fact that the technique is incredibly draining on those who performed it. Once the fusion ends and both fusees return to normal; they are left either unconscious or so tired they can barely move their body at all. After the fusion, a time limit of three days must be reached before the fusion can be attempted again.
Only those with pure intentions, for example, protecting loved ones, are able to use this method of fusion. If the intent is solely destructive and to gain extra power, the result will fail and the person in question will experience their blood vessels popping due to the fusion backfiring.