We combined the mutual information score and TF × IDF score (IR score) in order to select the best keyword translation in our transitive translation. The transitive translation used bilingual dictionaries to translate Indonesian query into Japanese keywords. The Japanese keywords are then used as the input to retrieve Japanese documents. The keyword selection is done in two steps. The first step is to sort translation candidates according to their mutual information scores calculated from a monolingual target language corpus. The second step is to select the best candidate set among 5 top mutual information scores based on their TF × IDF scores. The experiment against NTCIR-3 Web Retrieval Task data shows that the keyword selection based on this combination achieved higher IR score than a direct translation method using original Indonesian-Japanese dictionary and also higher than the machine translation result using Kataku (Indonesian-English) and Babelfish (English-Japanese) engines.