Rinkane 

Meguru Garai is a normal high school boy, except for the vivid dreams he has about a past life in a fantasy world. One day, a new transfer student, Kotaro Kongochi, suddenly arrived. Meguru found himself reunited with a friend from his dream life whom he thought he would never actually meet, but something was different about this Kotaro...? (Source: Comic Bushiroad, translated) Note: Chapter 12 was split into two parts and there are two bonus chapters.