Thetsu was abandoned by his Master a long time ago for embarrassing him during a meeting of martial artists. Thetsu however wasn't told anything, his sensei simply vanished during a journey they had embarked on together. Thetsu, a certainly optimistic young Vanara, figured this was a test and when he eventually arrived back at the monastery found that his Master hadn't returned yet. He was met with much derision from the other apprentices and the other teachers were aloof to his plight.
Eventually he decided to search for his Master on his own. This...did not turn out so well. Thetsu was relatively naive to the ways of the world and traveling without the wise warrior that was his superior was difficult.
After traveling to one of the more dangerous locations his Master frequented, the young Vanara was found by Dorla heavily wounded and saved his life. Thetsu here-forth abandons his quest to find his Sensei and swears a vow to help the clever alchemist accomplish her goals due to her life saving mixtures. In reality, he had lost hope in ever finding his old teacher and feels that aiding Dorla gives him purpose when he otherwise had none.