This paper presents the first results of a dark matter search using the WINERED infrared spectrograph at the 6.5m Magellan Clay telescope. The study focuses on detecting dark matter decaying into line photons with masses around 1.8–2.7 eV by observing dwarf spheroidal galaxies (dSphs) Leo V and Tucana II. The researchers used the WINERED instrument in the WIDE mode to collect data, employing a nodding technique to subtract background noise. They found some excesses in the data, which could indicate dark matter decay. By analyzing the data with zero consistent flux after sky subtraction, they established one of the most stringent limits on dark matter decay in the mass range of 1.8–2.7 eV. The results are robust as they do not rely on a specific background model and can constrain a wide array of photon-producing processes. The study also discusses the potential of using the James Webb Space Telescope's NIRSpec for similar searches. The results show that the dark matter decay rate can be constrained with high precision, and the data can be used to analyze various scenarios, including multi-body decays of dark matter and emissions from dark objects in dSphs. The study highlights the importance of further observations to confirm any excess signals and to improve the constraints on dark matter properties. The results are significant as they provide new insights into the nature of dark matter and its potential interactions with photons.This paper presents the first results of a dark matter search using the WINERED infrared spectrograph at the 6.5m Magellan Clay telescope. The study focuses on detecting dark matter decaying into line photons with masses around 1.8–2.7 eV by observing dwarf spheroidal galaxies (dSphs) Leo V and Tucana II. The researchers used the WINERED instrument in the WIDE mode to collect data, employing a nodding technique to subtract background noise. They found some excesses in the data, which could indicate dark matter decay. By analyzing the data with zero consistent flux after sky subtraction, they established one of the most stringent limits on dark matter decay in the mass range of 1.8–2.7 eV. The results are robust as they do not rely on a specific background model and can constrain a wide array of photon-producing processes. The study also discusses the potential of using the James Webb Space Telescope's NIRSpec for similar searches. The results show that the dark matter decay rate can be constrained with high precision, and the data can be used to analyze various scenarios, including multi-body decays of dark matter and emissions from dark objects in dSphs. The study highlights the importance of further observations to confirm any excess signals and to improve the constraints on dark matter properties. The results are significant as they provide new insights into the nature of dark matter and its potential interactions with photons.