For those who aren't train nerds, Nishi Oyama is the southernmost station in Japan.

I'm guessing it is a better use of time to return via roads to Kagoshima Chuo station and catch a train or plane. The end of the line terminates[1] at Makurazaki[2] station. I knew the route was a thing since seeing it[3] online, variants with seishun 18 kippu[4] (6 days) or premium seats[5] (10 days). It could be done in about 28 hours via 8 trains these days, including an overnight at Shin-Osaka. Jorudan prices it around 63,270 but doesn't offer all the different train options and Hyperdia's trying to convince me the route doesn't exist. I'm kind of surprised there isn't a certificate of completion for this route!

I spot checked my train reservations (I use spreadsheets to plan ticket/routes/reservations ) and think I've probably ridden at least half of these trains. Also wouldn't mind seeing a route over a holiday period to ride as many sightseeing trains as possible.

[1]
www.youtube.com/watch?v=WniYRFv6-TI

[2]
www.youtube.com/watch?v=UYOnxUDqjr8

[3]
www.youtube.com/watch?v=1i3OhYvHSDY

[4]
www.youtube.com/watch?v=LGaLkzyhxZ8

[5]
www.youtube.com/watch?v=x0WclJRiQN0&list=PLO4Mu4IWzuab0D2r7o3mmYV9 vWJY18H0c