frog1954Buy Keikyu ticket to Sengakuji (410 yen, I am afraid you must pay on cash--Japanese yen) at the ticket vending machine (Keikyu)
You can get a PASMO prepaid card at a Keikyu ticket vending machine
(from 1500 yen, including 500 yen paid as a deposit)
and use it to travel until Sengakuji Station (407 yen) or all the way to Higashi-shinjuku Station (614 yen). and the 72h Tokyo Subway Ticket at "Tourist Information Center".
This center is open until 1:00 (past midnight), while KEIKYU Tourist Information Center gets closed around 22:00.
The two information centers seem close to each other.
Haneda Airport International Passenger Terminal
- Introduction of Tourist Information Center http://www.haneda-airport.jp/inter/en/premises/service/rental_car.html...
- Map around Arrival Lobby on the 2nd floor http://www.haneda-airport.jp/inter/en/map/floormap/map.html?floorId=MA...
: On this Map,
@this information center is at the position of the green and lager question mark,
@and the Keikyu information center is around the position of the white and smaller question mark.
you can purchase a 72-hour Tokyo Subway Ticket on Day 2
at Laox Shinjuku Main Store (open from 9:00)
or Bic Camera Shinjuku East Store (in the shopping complex BICQLO, open from 10:00),
and start to use it shortly.
This option works well
especially when tourists are waiting in a queue in the center or,
when the departure of your last Keikyu train is approaching but you still can catch it if you skip the center.
The two large home electric appliance stores (mentioned above)
are each in a walking distance of Exit A1 of Shinjuku-sanchome Station.
You can take a train on the Fukutoshin Line
from Higashi-shinjuku (F-12) (departing at Track 1 or 2)
to next (F-13) Shinjuku-sanchome (arriving at Track 3)
(165 yen when you use a PASMO card).
On weekdays, this station is crowded during the morning commuters' rush. http://www.tokyometro.jp/station/yardmap_img/_station_%E6%96%B0%E5%AE%...
When you take this option,
you pay 372 yen (= (614 - 407 + 165) yen) more
compared to when you obtain a PASMO card and a Tokyo Subway Ticket in the airport and use them to get to Higashi-shinjuku Station.
In a case where you in the morning on Day 5 travel with this subway pass for three more times,
this option is logically better cost-wise,
on the condition that you don't use another pass.