Isekai Raku Raku Survival: Seizon Skill Tsuwamono no Ore ga Bishoujo Shiri to Kurasu Mujintou Seikatsu

It's been over 10 years since the teleportation device that transports people from Earth to another world was created. Satomi Kakeru is a high school student with survival knowledge and skills drilled into him by his grandfather, who lives in the mountains. Kakeru is transported to another world with 100 other aspiring adventurers of his generation to participate in training to become adventurers, but immediately afterward, the portal connecting Earth and the other world disappears...! With no way back to Earth, a dangerous life of survival begins on a deserted island in another world!