User blog comment:Master Sima Yi/Assassinews 12-05-'15 — Assassin's Creed: Syndicate has been revealed!/@comment-24760042-20150516222246/@comment-117.213.114.192-20150517073404

The reason he wears Indian clothes is probably because he wanted to kind of represent he was from India I guess. Sort of how Connor had feathers on his suit and a tooth necklace. Plus there were more than a few Indians in London most of them dressed in Indian clothes so it isn't really an uncommon sight.