One REIT, Inc., formerly SIA REIT,Inc. is a Japan-based real estate investment trust (REIT) company. It aims to achieve stable earnings and sustainable growth of its investment assets to maximize investment value from mid- to long-term perspectives, by investing in specific assets, including office buildings and commercial facilities in Tokyo metropolitan area, government-decreed cities and other major cities. Its investment properties included J Tower, SIA Kanda access, Central Shin-Osaka and fab Minami-Osawa, among others. Its asset manager is Simplex REIT Partners Inc.