Recommend this place. Great/ timely communication from Mayu & Tak. The place is very close to the Kamiyachō station (Hibiya line). The only drawback is that you may have to carry stroller, if you happen to have one, in order to go down to the subway. There is only stairs from subway to ground floor. This is not uncommon in many of Tokyo's metro stations, though.
Although the place can accommodate 8 people, I think it'd work better for 6 people if people want to hangout in public (non-bedding) area at night.