He is able to touch target(s) with his wakizashi and transport their consciousness' into his zanpakuto. By doing this, he literally sends an avatar of that person(s) into the spirit world of his zanpakuto to see within the deepest confines of his soul. Hoshiro, by use of this technique, enters into his inner-world himself as a host with the guest in tow. From there, he is able to control the inner world as he would had he been the only one there. While in use, both the target and Hoshiro are virtually helpless as their bodies are in a stasis. Only Hoshiro, while in this state, is able to end the session or if the avatar sustains damage that would normally kill Hoshiro or the guest. Energy used within the spirit world is expended normally as if the person had really been using the techniques. This technique is used normally as a training ground or a simulation room to prevent any real damage from being dealt.
First of all, I don't really feel comfortable with an ability that can allow other users to enter the inner world of your character, maybe this technique can create a virtual space that does much the same thing? But I don't like the inner world idea.
Second, the cost should be high for something like this, and it should have a post duration and cool down.
Third, does any damage done to them transfer to their outside bodies? And how limited would they be? Could they use Kido or would it just be strictly melee combat?