Confirmed at L1, on Haneda's own facilities page — the frequently repeated claim that this is only documented on blogs is wrong. Haneda publishes a dedicated page, ベビーカー貸し出し(空港内使用)/ 'Stroller Rental (for use within the airport)', and the BABY & KIDS GUIDE states it is free: 案内カウンター、チェックインカウンター等で貸出。(無料)— 'Free rentals are available at the information counters and check-in counters in Terminals 1, 2, and 3.' Locations as published: Terminal 1, 2F general area, 2 locations; Terminal 2, 2F general area, 2 locations; Terminal 3, 1F Entrance Plaza, 2F Arrival Lobby, 3F Departure Lobby, and 3F Airside Area (2 locations). Two caveats Haneda itself creates. First, the page's opening sentence frames the service as being for 見学・お見送りのお客さま — customers who are visiting or seeing someone off — while the BABY & KIDS GUIDE frames it as a general service; Haneda does not reconcile the two. Second, Haneda separately lists a 'Paid stroller rental (for use outside the airport)' as a distinct service, so do not confuse the two. No deposit, no time limit and no age or weight limit is published for the free loan.
Not published. No tokyo-haneda.com page states whether a private stroller may be taken to the boarding gate and gate-checked, or must be checked at the counter — Haneda treats this as an airline matter.