Originally Posted by
Nippon_Koukuu
In March, I checked my bags about 14 hours before my flight. I was flying on JAL intl J. My flight was technically the next day. I checked in around 11 AM and my flight was 1 AM on the next day. It wasn't technically overnight, but the date that I checked in was one day before the date printed on my boarding pass. So it might be possible to check-in the night before if you're flying on JAL. If your hotel is close to Haneda, I would say have a go at early check-in the night before.
That is because the shortly after midnight to around 1AM flights are counted to the flights of the day before. For a lot of them you will be required to check in the day before. Different setup, different options.