Reinen

Reinen (霊念, "Spirit Feeling") is the phenomenon of possessing a distinct nature, behavior, and characteristics. When reiatsu is sensed by, there are aspects to the materialized spiritual energy that can be perceived in different ways; physically, emotionally, and even functionally. This is what is referred to as the reinen, the component of reiatsu which embodies significance and identity. According to, Reinen is synonymous with , and serves as the foundation for higher-level.

Overview
Reiatsu is the emitted force from internal ; it carries the nature and intentions of its owner when materialized. As spiritual power is aligned to willpower, that means the force projected by it is also aligned with the will of the individual, and because of this, the characteristics it possesses is directly connected to their own nature. Reinen can induce physical sensations, in which the reiatsu is physically perceived in a certain way, while also being able to induce emotional sensations, such as instilling thoughts of despair or fear in opponents. It can also produce functional differences that set one's own reiatsu apart from others; examples of this can include elemental natures or even racial distinctions. In the case of the latter, this is seen prominently with and. For Arrancar, when they release their, their mixture of and  reiatsu transforms completely into Hollow reiatsu, while Visoreds attain a dual reiatsu when donning their masks.

When fought against, it was noted by  that the immense heat generated by the  could not possibly manifest as flames. Instead, he understood this to be the appearance taken by Yamamoto's overwhelming reiatsu in the Bankai state. Similarly, when released his Resurrección against, his reiatsu took on the form of a downpour of black rain; despite it not actually being liquid.

Role in Hakuda
In the higher levels of Hakuda, the concept of reinen is the basis for all techniques. The strength of a Hakuda specialist lies in reiatsu manipulation and control. When taken to a greater extent, even the nature of reiatsu itself can be altered. It is described as consciously shaping one's own willpower. In doing so, a Hakuda specialist at the Kiroku level can produce effects through their reiatsu that would normally be considered impossible. Seireitou's technique is said to be the highest level of reinen manipulation.