Denpa no Todoku Jikuu ni Imasu

Komada Tsukasa, a geeky nerd, and Endo Hayato, a good-looking athlete, have been childhood friends. Now in high school, they've become completely estranged, but one day, Tsukasa contacts Hayato on a favor and discovers he's in a surprising place - "Could this really be time travel?" His childhood friend's smartphone, which was sent to a different place in time and space, is still alive and able to communicate. When he receives images and videos, it seems Japan... or rather, could this scenery be "here" from the Sengoku period?! A Sengoku trip graffiti that connects across time!!

(Source: Shinchosha, translated)