Ryuuguu Gaimu ~Garasu no Naka no Tsubasa~

Sai and his sister, Ifa, grew up in the mountains of Szechuan. Their parents are dead. Ifa's lover, Koan, is a chips and offers to bring both of them to live in Eden. They both arrive in D. Zone as visitors and Sai is adopted by an old man, who teaches him how to be a pickpocket. Ifa is offered a counterfeit chip by a kind stranger, Hayami. She wanted Sai to go into Eden first but he told his sister that she should go ahead and be with her lover.

Ifa promises to earn money and get a chip for Sai when she can. But she disappears and was supposedly executed in a government crackdown on visitors with fake Chips, according to her lover who passed a bloodied chip (supposedly Ifa's) to Sai's guardian eight years ago. Sai goes on a journey (with a partner of your choice) to find Koan and about what really happened to Ifa.....

[From Aarinfantasy Forums]