If you are travelling to OpenStack Summit in Tokyo and have someone travelling with you who is not attending the conference, then you need to know about Spousetivities. The aim of Spousetivities is to enable those non-conference-attending people to have a good time while you are busy at the conference. Crystal Lowe organizes activities like day-long guided tours, one tour includes the Meiji shrine and the Ginza shopping district, another is to Mt Fuji. The sign up page is here on Eventbrite and the activities are open to all, no matter who is travelling with you they are all welcome to take part. The other place with lots of Spousetivities information is the facebook page.
From personal experience, I know that my wife enjoyed the Spousetivities activities far more than solo sightseeing when she travelled with me.
Spousetivites activities are subsidised by the support of sponsorship, do get in touch with Crystal if your organization would like to support Spousetivities.