The 104-times capped internationalist is a direct replacement for the injured Harlequins wing, who was ruled out of the tour with a knee injury sustained while representing his club in the European Rugby Challenge Cup Final.
Sean's inclusion is the second injury replacement to the touring squad this week, with Gloucester-bound centre Matt Scott coming in for Alex Dunbar, who injured his knee while representing Glasgow Warriors in the Guinness PRO12.
The Scotland squad will convene at BT Murrayfield Stadium on Monday 6 June for a short camp before their departure for Tokyo the following Saturday (11 June).
The Test matches – live on BBC – will be played on consecutive Saturdays at J1 League football stadia; the first at the Toyota Stadium in Toyota City (18 June), the second at the Ajinomoto Stadium in Tokyo (25 June), homes of Nagoya Grampus and FC Tokyo respectively.