At the end of a technique, the sword is re-sheathed (納刀). Most have been taught that Zanshin is maintained throughout. This is as part of a readiness of sudden changes of the situation and the sword be drawn again quickly. Although the idea is simple, many people don't fully understand this process. If you look carefully, most practitioners will have a more relaxed expression as the sword slides further into the Saya (鞘) and Zanshin diminishes. This reflects on one's state of mind. Strictly speaking, this is wrong. Your body may relax, but your spirit or mind should not.
A clearer way to express this is to re-think the process:
Re-sheathing the sword IS NOT to put it away. It is always at a state of readiness, be it in or out of the sheath, and so is your spirit.
Next time you perform Noutou (納刀), think about this.