Ah, if it's a JL F Domestic flight you'll get access to the Diamond Premier lounge (Domestic F lounge, same one OW Emeralds access). Having said that it's not a place with much to do or eat on a 5 hour layover.
https://www.jal.co.jp/jp/en/dom/serv...d/diamond.html
You'll still want to get something in the terminal whether that's fast food downstairs by the train station, or something more local in the upper levels of the terminal. Most of it is before security. There are a few eateries behind security, but not many. All of the variety is outside. Also HND domestic is extremely efficient, baggage cutoff is 30 mins, entering security is 20 mins before your flight and boarding close is 10 mins, so if you find something interesting to do away from the airport, go for it. Kamata station isn't exactly the creme de la creme of the city but it's only 10 minutes away and could easily occupy some time. You've also got Shinagawa station about 20-30 mins away, it's a business district but has some decent restaurants. Those are both direct shots out of the airport, Kamata is on Keikyu line, as is Shinagawa if you stay on the train a bit longer. The other train at HND, Tokyo Monorail doesn't go anywhere particularly interesting without changing trains.