Firstly I'll need to admit to being a cheap bastard.
I happily walk the 40 mins to Shinjuku rather than fork out the 290 yen for the JR/Tozai tickets. But the kiddies are back and the walking option is almost ruled out.
3 Eidan trains is 8 stops (190yen), but lugging half a pushchair in one arm and the FG 2 yr old in another up and down stairs on the ultra-kiddie-unfriendly Japan subway stations is not fun.
So the question: Can I zip out west to Ogikubo and transfer to the Marunouchi line without passing through a ticket machine?
(The Tozai fare chart only stretches to Nakano but the train goes all the way to Mitaka, going the other way through Otemachi is 15 stops and a long walk at Otemachi)