Hirotaka's place is in a great location which our teens really loved: if you know London, it's kind of a cross between Camden and Soho. Within just a couple of minutes you are right in the midst of things and Shibuya station, famous for its crossing (take photos from Starbucks!) is very close by.
The apartment itself is modest in size but this is more than compensated for by its location. It's also very well equipped and handily has a roof terrace if you need a bit more space. And, despite being in the centre of things and a few floors above a jazz bar, we didn't have any problems with noise at nighttime.
Getting in touch with Mariko (Hirotaka's niece who handled all our enquiries) was easy and straightforward (we met briefly and she was very sweet and friendly) - all in all, very happy to recommend.