Hi folks nice to meet you
The belief that there are specific "guides" or spirits that work with 'Reiki' and individual practitioners, is that the guides can be with us before we even initiate to into any healing approach. Some healing practitioners refer to these Guides as "Ascendant Masters", "Spirits", or "Guides". Some forgetting about tour Human Guides.
Also the belief in them varies to different beings that can come to help and support with Reiki and attuning. It is very important to be grounded when giving healing and sometimes guides will come a long to teach us this, from realms 'across the board' That means even a HUMAN guide that may have a special quality we can associate with.
I have found more and more often that many people are being taught Reiki without any information on working with the subtle bodies, or neutral approaches to healing and that of their guides. Not only can a guide come from spirit I feel, it can, come from many different places and being. Surly you have noticed the wind or the climate changing around you, when you are working at healing.
Reiki Guides may be present at attunement/initiation, when a person is given the Reiki Energy. This is performed by a Reiki 'Master' and attended and maybe guided by astral Guides, they do not have to have known or know Reiki. Reiki is a Japanese word for Universal energy. Some times, it has been said by my learning partners, this process of attunement/initiation seems controlled by forces beyond myself as the Reiki ''Master' the guide being free to influence an attunement/initiation and the Reiki 'Master' has no power over another's guides!
I hope that this helps
Warm regards of love light and laughter Gaynor AKA W*HolisticUK