Originally Posted by
hailstorm
Another alternative is to take the Hikari from Osaka/Kobe to Odawara, then transfer on the Shonan-Shinjuku line to Ikebukuro. Only one transfer, and slightly cheaper, and maybe a bit easier to get a seat from Odawara, though with a little bit less flexibility in the timing than the former method.
Having used the Shonan-Shinjuku line a few times recently, I have thought about the option but was too lazy to look up the timetable.
I have now looked it up and found that there's only one hourly train from Odawara going to Ikebukuro (and beyond). If you can find a good connection from the Hikari that should work but otherwise it will not be very convenient.
If you go as far as Shinagawa on the Shinkansen you have to take the Yamanote line to Osaki to change to the Shonan-Shinjuku line.
P.S. According to this
blog post (in Japanese) the Seibu buses which run between Haneda and Tokorozawa do have a toliet at the back.