I disagree. I can think of an extremely easy counter for this.
Even though no one came and asked me about this, I feel I still need to say something about this.
Lets ooks at the mayfly technique. Yes, it allows you to travel at extremely high speeds by meging your body with the ground/organic matter (which may include water). However, once you emerge from the water you still travel at normal speeds. Since the byakugan has a nearly perfect field of vision, he would see you the moment you begin to emerge from the water, and maybe even see your chakra as you move through the ground/water. On top of that you state that you stab him at the base of the neck, which is roughly 5 feet you need to travel to reach. In that amount of time he could easily see you moving upward from the ground and counter.
I think you are severly overestimating the power of mayfly.
Now sy you know the bolded and red is just not possible.. and as for the rest.. heres a copy and paste from my conversation with zen
Tom says
so space time, eig and sm are the only counters really then
Zenryoku Kaito says
well anything that can provide enhanced reactions and the ability to react with the visual side or sensory that aided with the speed to phsyically react
Tom says
so just doujutsu alone isnt enough
Zenryoku Kaito says
well a tomo 3 would require tai mastery
because uchiha arent actually able to react with their eyes unless their body can keep up
that is a key weakness to the sharingan
Tom says
byakugan offers no speed percetion so thats not much help
same with rinnegan
Zenryoku Kaito says
yeh that just gives a near 360 field of vision
rinnengan would only aide if with more than a pair of eyes are on the field
covering all angles
Tom says
k, thanks for clarifying
so no SY he cannot react in time but I appreciate your opinion