Yuko Thermal Straightening offered at Funké. Developed in Japan, Yuko Thermal Straightening changes thick, wavy or coarse hair to silky, shiny, polished locks. The best results are on virgin hair (no previous chemicals; color, perming, or straightening) with the process lasting from six to ten months. This process is not for all hair types, but we can tell in minutes if it's right for you.