I stayed at Mercure Hotel Haneda and overall had a pleasant experience, even though it was only for a short transit stay before my flight.
The room was very clean, well-equipped with an air purifier and complete amenities, including sleepwear provided in the room. I was lucky to get an upgrade to a king bed, which made the stay even more comfortable.
The hotel also offers a shuttle bus service, which is a convenient option. However, the shuttle only runs during limited hours—pick-up service from Haneda Airport is available in the evening, and drop-off to the airport is only available in the morning. Outside those hours, you’ll need to take a train or taxi.
That said, it’s still a solid choice for travelers—very clean, good facilities, and overall a reliable hotel near Haneda.