In the "Fist of the North Star" series, Toki is a skilled martial artist known for his healing abilities and his mastery of the Hokuto Shinken technique. The Ash of Death, a technique used by Raoh, does indeed have a profound impact on Toki. While he may suffer from its effects, Toki's strength doesn't necessarily diminish in terms of his martial arts skill; instead, the Ash of Death affects his physical condition and his overall health.
Toki remains a formidable fighter, but his battle against Raoh and the aftermath of the Ash of Death do take a toll on him, highlighting the tragedy of his character and the sacrifices he makes. So, while he continues to be strong, he faces challenges that weaken him physically due to the poison of the Ash.