General Strategies
236S/236K counter Option Select
An Option Select that takes advantage of GGST's Counter Hit system. By attacking with a medium strength or higher poke like 2S or 5H, then inputting 236S immediately followed by K, you will guarantee that on block or normal hit 236S will come out, while on counter hit 236K will come out. This is especially useful for Ky because 236K is rewarding but unsafe if blocked and very spacing dependent. In medium strength or higher counter hit slowdown, both hits of 236K will always connect regardless of spacing.
Pressure
Oki
Fighting Ky
Foudre Arc
Be sure to stand block Foudre Arc to ensure Ky gets as little frame advantage as possible from it. On standing block, it's -1, but on crouching block it's always plus. Ky's fastest jab is his 2P at 5f, and since he's -1 on block, if your character has a fast jab (<6f) you can interrupt his pressure. 6F jabs may clash with any followup Ky attempts. Keep in mind that if you're hit by Arc while in Shock State (or Ky is in Dragon Install), he will always be at advantage, even if stand blocked.
Stun Edge
Utilizing short forward dashes into block is a common strategy to close the gap against an opponent that utilizes lots of projectiles. However, Ky's Stun Edge will inflict Shock State on the defender even on block. Consider using other options to close the gap more often than you would against other characters. One weakness of Stun Edge is that it leaves Ky vulnerable to counter-hits during the recovery frames. Experiment with your character's options to find a way to exploit this. Sol's Night Raid Vortex can low-profile under Stun Edge and punish the recovery frames. If Ky uses Stun Edge at full screen, you can punish with Night Raid Vortex on reaction. Nagoriyuki's Zarameyuki beats Stun Edge, allowing you to deal damage to Ky and build Blood Gauge. With enough Blood Gauge, 5H becomes large enough to contest Stun Edge during the start-up.