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Young solar-type stars frequently produce superflares, serving as a uniquewindow into the young Sun-Earth environments. Large solar flares are closelylinked to coronal mass ejections (CMEs) associated with filament/prominenceeruptions, but its observational evidence for stellar superflares remainsscarce. Here, we present a 12-day multi-wavelength campaign observation ofyoung solar-type star EK Draconis (G1.5V, 50-120 Myr age) utilizing TESS,NICER, and Seimei telescope. The star has previously exhibited blueshiftedH$\alpha$ absorptions as evidence for a filament eruption associated with asuperflare. Our simultaneous optical and X-ray observations identified threesuperflares of $1.5\times10^{33}$ -- $1.2\times10^{34}$ erg. We report thefirst discovery of two prominence eruptions on a solar-type star, observed asblueshifted H$\alpha$ emissions at speed of 690 and 430 km s$^{-1}$ and massesof $1.1\times10^{19}$ and $3.2\times10^{17}$ g, respectively. The faster,massive event shows a candidate of post-flare X-ray dimming with the amplitudeof up to $\sim$10 \%. Several observational aspects consistently point to theoccurrence of a fast CME associated with this event. The comparative analysisof the estimated length scales of flare loops, prominences, possible dimmingregion, and starspots provides the overall picture of the eruptive phenomena.Furthermore, the energy partition of the observed superflares in the opticaland X-ray bands is consistent with flares from the Sun, M-dwarfs, and closebinaries, yielding the unified empirical relations. These discoveries provideprofound implications of impact of these eruptive events on the early Venus,Earth and Mars and young exoplanets.

Multiwavelength Campaign Observations of a Young Solar-type Star, EK Draconis. I. Discovery of Prominence Eruptions Associated with Superflares