Seishun 18 ticket! I’ve read that it’s popular with the locals, but us foreigners have the JR Pass.
As for why it’s “gutsy”, you can only take regular “local (普通, 快速, etc.)” trains with it (no limited express or Shinkansen), so getting from Tokyo to Nagoya using it would not be comfortable and isn’t something people would normally do. It would take approx. six hours with around four transfers.