The Sharingan bonus is a flat +6 to a variety of rolls where it makes sense to be applied
Whoops. On the other hand, wow, baby Uchiha are
monsters, compared to their age level. Bloodlimits are really unfair. Also, we need to light some incense for Obito. (Unrelated: How old is the Uchiha heir? I'm trying to calibrate my screaming in Kagome)
So, here's a worked example, between Kakashi and his Chair-ignoring evil twin Shikaka, who put those 116 points (and ten more) into three levels of Alertness. All rolls are +0, but they don't know that. They both start with no FP and infinite chakra.
Alertness v. Alertness, S wins.
Athletics and Strong Fist v. Athletics, S wins by +6
Tai v. Tai, S wins by two shifts, plus one for ninja hands, K takes three stress.
K does the same to S.
Round Two:
S does the same thing, the three shifts of stress make K fill out his last stress box.
K does the same, S takes a moderate consequence. All his (relevant) roll are now -6, but he gets an FP. K gets a tag on S.
Round Three:
S wins Strong Fist by +0, and spends his FP on Tai to do as much damage as he can. Five shifts of damage, except that K used his tag. Three shifts, moderate consequence. K gets FP and -6, S gets tag.
K wins Strong Fist by +6 (+0 if S spends his tag, which would be dumb). K spends his FP on Tai, will do a Severe. S spending his tag would be unwise. S now is at -18 and has a tag and a FP.
Round Four:
S goes for Strong Fist and loses. Spending his FP and/or tag here would be wasteful. He uses both instead to cancel out the -12 he just received, and does two shifts to K, a Mild. K at -9 and 1FP, S has tag.
K goes for Strong fist and wins easily (+15). He punches, using his FP. S uses tag to counter. Still does six shifts. S is Taken Out.
I think. I may have misunderstood the rules around tags, D20 is my main base of understanding.