If the item was lost during an official grand tournament at Ryogoku Kokugikan, the arena’s official page directs you to the Japan Sumo Association at 03-3623-5111. If it was lost during a concert or another venue-hire event, contact that event’s organiser. Do not use the Kokugikan venue-hire form for a honbasho lost-property enquiry.
The realisation often arrives on the train: the binocular case is empty, the paper banzuke has vanished, or the souvenir that survived a crowded concourse is not in the bag. It can make a wonderful day feel suddenly fragile. A useful response has two parts—send the enquiry to the organisation that operated your event, then describe the item well enough to distinguish it from every other black umbrella or phone case.
The building does not determine the lost-property desk
Ryogoku Kokugikan hosts sumo tournaments and separately hired events. Its official contact page specifically says that operational and lost-property matters during a honbasho should be directed to the Japan Sumo Association on 03-3623-5111. Lost property during another event should go to that event’s organiser.
Check the event name on your ticket or booking before contacting anyone. A grand tournament and a concert may share the building but have different enquiry routes. The Kokugikan venue-hire form is for venue-hire enquiries, not lost property.
Prepare five details before calling
Write down the date, approximate time, seat or section, last known location and a distinctive description. A strong report is more precise than “black binoculars.” It might say: “September 18, second-floor chair section, used before the makuuchi ring entrance, black fabric case, white mark on the strap.”
Reconstruct the route only as far as you genuinely remember: seat, restroom, shop, museum, exit. Include a name or serial number if one is attached to the object. Keep your ticket information available, but do not post a QR code, full seat detail or personal identity document publicly in the hope that social media will solve the problem.
A lost admission ticket is an urgent, separate problem
If you lose your ticket or the phone that displays your QR before entry, contact the ticket seller and explain the situation to staff at the event. Have your booking details ready. Reporting an item lost does not itself establish permission to enter.
Keep a paper ticket or stub in its usual place until you leave. For Ticket Oosumo QR tickets, a screenshot or printed image is not accepted for admission. If you rely on your phone, allow enough battery for the whole visit.
Ask how to collect a recovered item
When you enquire, ask what proof of ownership is needed, where an item can be collected and how long it is kept. If you need it sent to you, ask whether that is possible and what it costs. Do not arrange collection or assume postage until the contact confirms the item and the procedure.
If a Japanese-language call is difficult, a hotel front desk or Japanese-speaking companion may be able to help communicate. That is a practical suggestion, not an official translation service offered by the Association.
A ten-second check before leaving
Before standing up for the final time, touch three things: ticket phone, wallet and main bag. Look behind the seat and at the boundary with the next box. The check does not interrupt the magic of the day; it helps the paper banzuke, with all the noise folded invisibly inside it, make the journey home too.
Sources checked
Checked October 8, 2026: contact routes, presenting and retaining a valid ticket, and Ticket Oosumo QR guidance.