This will be a First-in-Human, Phase 1, multi-center, non-randomized, open label study of DS-3201b, Histone-lysine N-methyltransferase EZH1/2 dual inhibitor to assess its safety and tolerability, identify a maximum tolerated dose (MTD)/ tentative recommended phase 2 dose (RP2D), and assess its pharmacokinetic/dynamic properties in Japanese subjects with Non-Hodgkin's Lymphoma.