GRAINE project aims at precise observations of cosmic gamma rays from sub-GeV to GeV, especially on the Galactic plane or central region, using a balloon-borne nuclear emulsion telescope with a large sensitive area, high angular resolution, and polarization sensitivity. So far, the balloon experiments have been performed in 2011, 2015, 2018, and 2023. In the 2018 flight, we successfully imaged Vela pulsar with the highest angular resolution. In the 2023 flight, we employed a large sensitive area telescope, 6.5 times larger than in the 2018 flight. To increase the area and the number of flights for large statistics, one of the most important development elements is to speed up the readout system of nuclear emulsion. The nuclear emulsion records all charged particle tracks as analog images. The images should be readout by a microscope and analyzed using huge computer systems. We are currently developing a next-generation nuclear emulsion readout system, Hyper Track Selector 2 (HTS2). The designed scanning speed is 5 times faster
than that of the previous system (HTS), which was developed as the fastest readout system in 2015. In this presentation, we will give an overview of the developments and features of HTS2. In addition, we will give the latest scan data obtained with HTS2.