Since the discovery of neutrino oscillation in 1998, an overall picture of the flavor-mass mixing in the lepton sector has been build. Compared to those in the quark sector, the mixing angles are large and squared masses are much smaller. Missing in the picture is the CP phase and the ordering of masses. With the large mixing angles, the size of the CP violation, Jarlskog invariant, in the lepton sector can be three orders of magnitude larger than that in the quark sector. In this talk, I will present the latest status of the CP phase measurement by the T2K experiment and the prospect of T2K and the Hyper-Kamiokande experiment. If there remained time, I would also like to introduce my another activity on a xenon gas time projection chamber for the neutrinoless double beta decay search.