Anonymous former Japan former Maritime Self-Defense Force officials told the Asahi Shimbun that the Izumo-class helicopter destroyers were design to operate short take-off and vertical landing (STOVL) fighters from the beginning.
By Kaijō Jieitai （海上自衛隊 / Japan Maritime Self-Defense Force） (http://www.mod.go.jp/msdf/formal/jmp/201612.html) [CC BY 4.0], via Wikimedia Commons
One person said during the design phase of the ship, consideration was given to have the F-35B operate from the Izumo someday.
The former MSDF executives added that a skijump was to be added when the ship is required to operate the F-35B.