I got the latest Pathfinder setting book, Inner Sea Gods, and hey, look who turned up? It’s Master Roshi!
Mythology Pro Tip: this guy is based off the Japanese legend of Urashima Tarō. Tarō was a man who (long story short) saved a small turtle who was actually the sea emperor’s daughter. He visited a palace at the bottom of the sea on the back of a larger turtle and when he returned, what seemed like a few days later, 300 years had passed. He then opened a magical box the princess had given him, which properly aged him, turning his beard white and bending his back.