Name: Ken Kaneki
Species: Artificial One-Eyed Ghoul
Age: 23
Rating: SS
Abilities: Master Swordsman, Yukimura 1/3, Rinkaku, Kakuja, Martial Arts expert, Great regeneration, Highly intelligent, Excellent stamina, excellent durability, excellent strength, excellent speed
vs.
Name: Gotou
Species: Parasite
Age: 48 (Human Body)
Rating: Strongest Parasite
Abilities: Shapeshifting, Complete body manipulation, 5 parasites that he can control at once, highly intelligent, excellent stamina, excellent durability, excellent strength, extremely high regeneration, excellent speed
Scenario: Both are bloodlusted and have all abilities from their respective anime / manga. No restrictions. For the sake of the battle, let's assume Gotou can sense Kaneki similar to how he can sense other Parasites.
Location: On the rooftop of a large city building, no one else is around and the encounter is random. They start 20 meters from each other.