The Yokote is the separation between the Kissaki (the tip) and the rest of the blade. It is the line of separation. Most Katanas have this Yokote, but there are specific blades that do not have a Yokote.
This Yokote is not only aesthetic but also has a function to make the tip stronger and more effective in piercing a target. The impact will be wider and bigger. This part is historically very useful to pierce a samurai armor for example.
The Yokote allows dissipating the shock, to absorb it and also to solidify an impact, especially when it is frontal to pierce a target.
For a high-quality blade with a very well worked geometrical Yokote, you should look at Katanas at around $1000