Flying raijin, or hiraishin as its more commonly known, is instantaneous. Logic, even manga wise, doesnt permit us to allow the possibility of things like neck, feet and hand movement to be faster. Any amount of speedy reflexes or movements still have to cover a set distance, and therefore consume a set amount of time. A sword thrust to impale a shinobi from behind their back may appear instantaneous, but in reality is much slower than true instantaneous shifting (calling the hiraishin 'movement' would be inaccurate, as there isnt any involved, rather an object starts to exist from point 'a' to point 'b', overlapping two spaces with a given mass, covering a physical space in zero time, hence its categorization as a space time ninjutsu).
In theory, not only would it be impossible for someone to react to this, but faulty shifting could cause scenarios in which the overlapping causes semi comical errors, such as say minatos arm appearing inside his opponents chest lol. But as this is the manga, we'll have to set that aside.
To clear up the popular misconception that madara uchiha boosted by senjutsu reacted to hiraishin, note that:
- in the first instance he was surprised when tobirama appeared behind him. THAT was hiraishins speed.
- he then bent his neck to the side to avoid tobiramas sword THRUST, that was a physical movement made by the 2nd AFTER he used hiraishin
- madara then proceeded to disarm him with his taijutsu, and tried to stab him with his black rod
- then hiraishin allowed tobirama to appear a small distance off to his side, that caught madara even in that state by surprise.
-the 2nd charged at him with his kunai
In no instance was madara able to react to the hiraishin itself, what he did was to use his enhanced base speed to ward off tobiramas physical attacks after he had manifested himself, the distance between the physical space to which tobirama teleported and his intended target (madara) was too great.
Minato, the other user of hiraishin, is able to close that distance a notch so that his attack lands almost as soon as he reappears (as we all saw when he struck obito during the kyuubi invasion of konoha). And thats how his ftg is superior to tobiramas, not because its faster (which is impossible in any case), but because he can control it better to appear closer to his intended target.
Hope that clears some things up.
In theory, not only would it be impossible for someone to react to this, but faulty shifting could cause scenarios in which the overlapping causes semi comical errors, such as say minatos arm appearing inside his opponents chest lol. But as this is the manga, we'll have to set that aside.
To clear up the popular misconception that madara uchiha boosted by senjutsu reacted to hiraishin, note that:
- in the first instance he was surprised when tobirama appeared behind him. THAT was hiraishins speed.
- he then bent his neck to the side to avoid tobiramas sword THRUST, that was a physical movement made by the 2nd AFTER he used hiraishin
- madara then proceeded to disarm him with his taijutsu, and tried to stab him with his black rod
- then hiraishin allowed tobirama to appear a small distance off to his side, that caught madara even in that state by surprise.
-the 2nd charged at him with his kunai
In no instance was madara able to react to the hiraishin itself, what he did was to use his enhanced base speed to ward off tobiramas physical attacks after he had manifested himself, the distance between the physical space to which tobirama teleported and his intended target (madara) was too great.
Minato, the other user of hiraishin, is able to close that distance a notch so that his attack lands almost as soon as he reappears (as we all saw when he struck obito during the kyuubi invasion of konoha). And thats how his ftg is superior to tobiramas, not because its faster (which is impossible in any case), but because he can control it better to appear closer to his intended target.
Hope that clears some things up.