Young's apartment was an amazing experience!
The location was very good, in a residential area close to Shinjuku station (20 minutes walking) with good connection to metro or train stations. Also is pretty big considering Tokyo standars, so for two people is excelente, perhaps for three persons would be small. It was very clean and tidy, with a lot of tourist information and Tokyo guide books to move around.
If IU ever go back to Tokyo, I would book again in Young's apartment. Highly recomended!