{112-2} twinning commonly takes place in α-titanium (α-Ti). High-resolution transmission electron microscopies (HRTEM) explored various steps along {112-2} coherent twin boundary. Topological model of {112-2} twin revealed twinning disconnections (TDs) that are represented by (bi, ) corresponding to a step height and a shear vector bi. Atomistic simulations were conducted to study the energies and kinetics of TDs. Combining microscopies and atomistic simulations, we concluded that (b3, ) is the elementary TD and (b1, ) is the reassembly TD. Steps observed in HRTEM thus can be treated as a reassembly of (b3, ) TDs and (b1, ) TDs. In addition, Electron Backscatter Diffraction (EBSD) maps revealed {112-2} → {112-1} double twins in α-Ti. Using two-dimensional and three-dimensional atomistic simulations, we demonstrated the nucleation of (b1, ) TD and → double twin through the interaction between basal dislocation and {112-2} twin. Our results enrich the understanding of {112-2} twinning including TDs, steps, and {112-1} secondary twins in hexagonal metals.