At first, the story seems confusing, because the artist didn't show the time skip clearly. On chapter 1 page 8, it says the exhibit runs from "(2015.)11.8 - 2016.1.10", then on chapter 1 page 17, someone is heard on the radio saying "back in 2017", and later Kazushi mentions a memory from 3 years ago, so there must be a 3 year gap between their meeting (page 13) and current time (page 14). Chapter 2 explains what happened between pages 13 and 14 of the first chapter (when Rui recalls their meeting at the exhibit, as Kazushi sleeps soundly), as well as the reasons why it happened, and foreshadows of an impeding separation between them.
Saihyou to Tokeru