The Hiroshima Carp announced on May 18 that Kris Johnson will be returning to the United States on May 19 for the birth of his first child. He is scheduled to return on May 30.
[UPDATE 6/4 @ 3:44am]
Johnson returned to Japan on May 30. He started a Ni-gun game against Chunichi on June 3 and gave up two runs on five hits over four innings. He threw seventy-one pitches, faced eighteen batters, struck out six, and topped out at 148km/h. He could rejoin the Ichi-gun team in time for the Rakuten series that begins on June 8.
Source: Daily Sports 6/3/2018