Regulatory subunit of the condensin-2 complex, a complex that seems to provide chromosomes with an additional level of organization and rigidity and in establishing mitotic chromosome architecture (By similarity). May promote the resolution of double-strand DNA catenanes (intertwines) between sister chromatids. Condensin-mediated compaction likely increases tension in catenated sister chromatids, providing directionality for type II topoisomerase-mediated strand exchanges toward chromatid decatenation. Required for decatenation of chromatin bridges at anaphase. Early in neurogenesis, may play an essential role to ensure accurate mitotic chromosome condensation in neuron stem cells, ultimately affecting neuron pool and cortex size (PubMed:27737959). Seems to have lineage-specific role in T-cell development (By similarity). Component of the condensin-2 complex, which contains the SMC2 and SMC4 heterodimer, and three non SMC subunits, NCAPG2, NCAPH2 and NCAPD3 that probably regulate the complex. Defects in Ncaph2 are the cause of the nessy phenotype which is characterized by a specific defect in T-cell development. Nessy thymuses are smaller, with corticomedullary junctions less well defined, and cortical cells sparser than in wild-type. The thymocyte defect is typified by an increased proportion of CD4-CD8- DN T-cell progenitors. Only thymocyte differentiation is affected in Nessy mice and not cell differentiation. Belongs to the CND2 H2 (condensin-2 subunit 2) family. Truncated N-terminus.