This research work describes a machine translation system from Japanese to Sinhalese (The National Language of Sri Lanka). This work can be introduced as the first effort on Japanese-Sinhalese machine translation system. The research proposes a method of analysis for Sinhalese morphological structure which shares features with Japanese, and makes an investigation into contrastiveness between Sinhalese and Japanese. Then it proposes translation solutions for Japanese function words after predicates and nouns. The first stage of the system processes the translation of propositional content. The clarification of case markers correspondence is handled in this stage. The second stage covers the translation of tense and modality, which are expressed by function words after the predicate in Japanese. Japanese short sample sentences were translated into Sinhalese with this system and its effectiveness was confirmed.