Most of the time Accellerator undoubtly relies on an automatic field surrounding him (whether it actually requires touching or not). You can't actively deflect bullets. From a human perspective, a bullet hits you the same moment it's shot - there's no time to actively reverse its vectors. The speed is high enough for that. Even assuming Kihara has godly precision to use that autamatic deflection like that to his own ends, the weakness of the fight lay in the fact Accelerator did nothing at all to actively counter the strategy.