The play is an American play that was made into a Hollywood film of the same name. It is a love comedy about a 40 year old woman that on a vacation in Greece meets up with a younger man and they sleep together. She leaves for home in the U.S. then and discovers that the man her daughter is dating is the same guy she slept with.
Yahoo! Japan article (Japanese)
From what I have read of the story for the play Yabu will be the young man and Uekusa the ex-husband of the main character.
Overall I am just happy that Yabu is getting some work. And he does not have to be stuck in the youth image that Hey! Say! JUMP just cannot seem to shake.