This sentence requires the subject pronoun for 'they' in German. 'Sie' (capitalized) means 'they'. 'Ihr' is 'you (plural)', 'Er' is 'he', and 'Du' is 'you (singular informal)'. The sentence translates to 'They are in Tokyo.' The capitalization of 'Sie' distinguishes it from the lowercase 'sie' which can mean 'she' or 'they'.