With seven hours between flights, you can't expect much. A visit to Narita City would offer a glimpse of a small town. A possible alternative would be to visit an onsen. Your friend could catch a free shuttle bus from NRT T2 to Sora no yu for some time in an outside bath while plane spotting and a bite to eat.
https://soranoyu.com/en/access#shuttlebus

As someone else suggested above, it's also possible for your friend to visit central Tokyo. For example, they could take the monorail, then the Yamanote line to Ueno. Walk to Keisei Ueno station to put luggage in a locker and purchase a Skyliner ticket to NRT. Then wander around Ameyoko or Ueno Park. This is doable but it involves hauling luggage around some busy stations, which might be more stressful for a first time visitor. Is it a better "taste of Japan" than a visit to Narita? I think that's down to personal preference.

One thing that you might want to check is the operating hours of check in for your friend's onward flight.