Shinjuku Station and luggage: there is a strategy, and it is not obvious from inside the station

Shinjuku Station processes more passengers per day than any other station on earth. It has around 200 exits by some counts. Nobody who tells you that prepares you for the practical reality of arriving with a 26-inch rolling bag and needing a large locker before noon on a summer Saturday.

The actual locker situation

Large lockers — the ones that take a full-size rolling bag — cost ¥600–800 per day. IC card payment is standard at banks built in the last decade; coin-only machines survive in older sections. The midnight-reset rule applies everywhere: your rental window is calendar days, not 24-hour periods. Arrive at noon, collect at midnight — one day. Leave your bag at 11:30pm, collect at 12:30am — two days.

The problem is availability. At the JR South Exit locker banks and the cluster near the Odakyu ticketing gate, large lockers are gone by 9:30–10am on busy days. I've arrived at 10am on an August Tuesday and found three banks fully occupied.

Where to actually find lockers in Shinjuku

The banks that fill fastest are the ones you walk past immediately after clearing a major ticket gate. Everyone goes there. The ones that stay available longer:

The subterranean connector level between the JR gates and the Metro stations — specifically around the passage connecting toward Marunouchi and Keio. Less foot traffic because it's a through-route, not a stopping point.

The Odakyu Department Store B1 level, east end — accessible from the street without going through the main gates. Fewer large lockers but usually one or two free mid-morning.

The western side of the station around the Metropolitan Government building exit — this section is genuinely less trafficked and holds out longer.

If you're flying into Haneda or Narita and heading directly to Shinjuku with full bags, plan 15 minutes for locker hunting. That's not paranoid, it's realistic on a summer weekend.

For the full spread of locker banks including the overflow locations most travelers don't find, there's a map and breakdown here:

https://tabi22.com/coin-locker-japan-shinjuku/

The forwarding alternative

If your next stop is another hotel and you're there more than one night: Yamato forwarding from the hotel front desk before 10am is often cleaner than the locker calculation. ¥1,500–2,000, bag appears at check-in next day. The locker math only wins if you need same-day access.

Anyone sorted out a reliable Shinjuku bank for large bags that doesn't require arriving before 9am? The western exit section is my current answer but I wouldn't call it settled.