It may be better to stay overnight in Kawaguchiko area.
I think the JR East pass is our best plan with 5 days. Yes.
As you know, a JR East Pass is a flexible 5-day pass which can be valid on 5 days in total during 14 consecutive days. It can cover Aoimori Railway line but it does not cover Fuji Kyuko [Fujikyu] line.
You can use a JR East Pass
on 5 and 6 August (for Airport Terminal 2 -- Tokyo -- Sendai -- Shin-Aomori -- Aomori -- Misawa),
on 11 August (for Misawa -- Hachinohe -- Omiya -- Nagano),
on 12 August (for Nagano -- Matsumoto) (for Matsumoto -- Otsuki)
and on 13 or 14 August (for Otsuki -- Shinjuku).
You had better expect at least 15 minutes for the transfer to Tohoku Shinkansen in Tokyo.
In Tokyo, Sobu Underground tracks for trains from/to NRT lie under the ground on the 5th basement and near the Marunouchi end, while Shinkansen tracks lie above the ground and near the opposite Yaesu end. JR-East and JR-Central have Shinkansen zones separately. JR-East Shinkansen tracks are Tracks 20 - 23. Please pay attention to names of Shinkansen lines on signboards so that you can smoothly find a correct Shinkansen transfer gate.
- Tokyo Sta. of JR
https://www.jreast.co.jp/e/stations/e1039.html: Sobu Underground tracks on the 5th basement (B5) are shown in the map around its bottom. You can get to the ground concourse using a short escalator first, a long escalator second and another escalator third. Then you can proceed on the pathway until you pass by a staircase up for Tracks 9 and 10, go up a short staircase on the left, proceed a little more and find JE-East Shinkansen central transfer gate on your right.
Tokyo Bay hotel late arrival Which area will you stay?
If you stay in a hotel near a station on Keiyo Line (except Tokyo Station), you can avoid a long transfer to Keiyo Line in Tokyo Station by traveling from Shinjuku Station through to Shin-kiba Shinjuku Station on JR Saikyo Line + TWR Rinkai Line (via Odaiba area).
