Yuta Notsu is studying stellar magnetic activities especially "superflares" on solar-type (G-type) stars and cooler K,M-type stars, using the various photometric and spectroscopic data from space and ground telescopes (e.g., Kepler, TESS, APO3.5m, SMARTS1.5m, NICER). Through these observational studies, I investigate how frequently superflares occur on G,K,M-type stars, how large superflare events occur in the stellar atmosphere (photosphere - choromosphere - corona), and how planets (e.g., Earth, Mars, exoplanets) are affected from these flares. Recently, he also newly joined MAVEN EUV team in LASP.