Ookina Enban no Shita de

Beneath the Giant Saucer

16-year-old Inami Nitta suddenly regains consciousness on top of a mountain and tries to figure out what has happened to him, be it the loss of his memories of the previous month, the flying saucer he constantly sees out of the corner of his eye, the strange barrier that protected him from a car crash, or the odd behavior of his classmate!

(Source: MANGA Plus)