TNK Co., Ltd. is a Japanese animation studio located in Nerima, Tokyo Prefecture. It was established on January 29, 1999 by Nagateru Kato, a former producer from Tatsunoko Production. They have produced a number of series to date, most notably their adaptations of School Days and High School DxD, among others such as Hand Maid May, I My Me! Strawberry Eggs, UFO Ultramaiden Valkyrie, and Kannazuki no Miko.