In truth, this was not something Shiro had prepared only for Kakashi and the others. Recently, Shiro had rushed out quite a few of them and given them to some of the friends he was close to.
But in reality, the thing was not all that useful. It could only be used to save a life.
Because while, in theory, it could be released, in practice it could not. Releasing a Noble Phantasm was not as simple as just calling out its true name.
Take the simplest beam attack, for example. It looked like nothing more than a long pillar of light that you could simply swing out, but in reality, there was a lot of nuance to reciting the true name, as well as the angle of the swing, the energy poured into it, and so on.
More importantly, Shiro's Noble Phantasms were only Projections. They could not be transferred, which meant others could not hold on to them for long.
They could only use them in the instant the seal was released, so the limitations were still very severe. Because of that, Shiro had not put much thought into it. He had only sealed a medical Noble Phantasm for them to use to save their lives, and that was that.
After all, they could not handle the other ones anyway. The reason Shiro could use them freely was that projected Noble Phantasms came with their original owners' combat techniques, and other people did not get that benefit.
Therefore, based on that point, Kushina and the others had only developed it this far. Going any further would not be worth it. Even if they could break through this limitation, Shiro could not spend every day doing this, could he?
Of course, even just this much could turn around many