On my itinerary, I mentioned that I have the whole Friday free for loitering around Tokyo. Was suggested by a friend to take the daily JR pass for around 700 yen or so which she says covers the Yamanote line for the whole day and her mentioning it covers Shinjuku, Shibuya, Harajuku, Asakusa and the likes, fit for a day of loitering. Did a bit of googling and I would assume what she meant was the JR Tokunai Pass for 750 yen. Looks and sounds kinda OK to me. Is there any drawbacks to this that I am not aware of?