We seem to have a romanji meltdown here. I would pronounce "Tach"
like the first part of "Taco" or "Tak" So I would think that Japanese
would pronounce it "Taku" (which sounds a lot like otaku:-))However, if
it is "Tach" with an actual ch sound then Japanese would probably
pronounce it "Tachi" which is the principle's nickname for Tatewaki in
cannon anyway. Tach with a k sound make sense to me as it could be short
for Tachometer, a device for measuring speed of rotation (gelling with
the skateboarder aspect of the new character) or even Tachyon, a
nonexistent particle in Star trek responsible for time travel.
Since at least part of this fic deals with the clash of American
and Japanese cultures it might actually be a good idea to put some of
this confusion into the fic.
A suggestion:
In that case, then you may want to bring up the difference between how he
pronounces it and how it is written. So far, you have had him say his own
name and the people he is talking with are hearing "Taku". By having him
write out his name in romanji for the class to see, you'll introduce some
of your proposed confusion since the students (and maybe even the teacher)
would see "Tach" and think it is pronounced "Tachi".
Master Pivot