Following a messy divorce, Jack Shephard traveled to Phuket and encountered Achara on the beaches there. Helping to assemble his kite, the pair sparked a relationship immediately, with Achara handing Shephard a small, rectangular object as a gift. Beginning an intimate relationship, Achara remained mysterious, coming and going from Shephard's hut with out explanation. Suspicious and slightly intoxicated, Shephard followed her following one of their meetings and discovered that she worked as a tattoo artist. Asking her to brand him with her work, Achara declared him an outsider and claimed that she could only mark natives. She described the body art as definition as opposed to decoration, claiming to "see who people are" and then tattooing that on them. Forcing her hand, she claimed there would be consequences as she inscribed the phrase "He walks amongst us, but he is not one of us." According to Achara, it signifies that he is a leader, but that being one makes him "lonely, and frightened, and angry". ("Stranger in a Strange Land")
In the following days Achara's brother, Chet, discovered the transgression that had occurred and hunted down Shephard and beat him severely with the help of several Thai men. Sufficiently battered, Shephard was warned that if he ever returned he would suffer greater consequences, watching a sad Achara turn her back on him as she sailed away. ("Stranger in a Strange Land")
The mark of Dharma is Achara or good conduct. Achara is the mark of the good. From Achara is Dharma born. Dharma enhances life. Man attains prosperity and fame, here and hereafter, through the practice of Dharma". 
In the May 11, 2007 Lost Podcast, Damon Lindelof and Carlton Cuse joke that the shark swam all the way to Thailand and forced Achara to give it a DHARMA tattoo or it would "bite her head off". Achara is one of 2 minor characters to have their name appear in a soundtrack title.