It originates from the Tomari-te school and in modern karate is practiced in Shorin-ryu, Shito-ryu, Shotokan, Genseiryu and Matsubayashi-ryu.
Karate master Shoshin Nagamine considered wankan to be his favorite kata.
A quote from his book describes the kata as "Being characterized by unitary sequences of attack and defense".
[1] About Wankan, Nagamine Shōshin (1978: 240) said: This kata is said to be the creation of a master in ancient times, but the creator is unknown.
Wankan is also known as Matsukaze (松風 or "pine tree wind") in some schools of karate.