Rail Pass usage in excess of area of usage

Using the Sanyo-San'In Area Pass going to Kotohira by limited express, am I correct in assuming that I'd only have to pay the equivalent of a ticket from Sakaide to Kotohira on a limited express (1350yen) and alighting at Kotohira, all I have to do is show them the rail pass and surrender the previously-bought ticket from Sakaide to Kotohira? I usually don't extend my travels past the area of coverage, so I am not well-versed in these instances. Thank you.

Your assumption is almost correct, except that the last station covered by the pass will be Utazu rather than Sakaide. Therefore, the supplement fee is only 690 yen on an unreserved seat. The cost for a reserved seat is around 1500 yen (it varies by a few hundred yen depending on travel date).

Thanks Uji. So if I were to take a limited express train from Okayama directly to Kotohira, it would be better to buy the reserved ticket from Utazu to Kotohira instead of from Sakaide to Kotohira? Thank you.

So if I were to take a limited express train from Okayama directly to Kotohira, it would be better to buy the reserved ticket from Utazu to Kotohira instead of from Sakaide to Kotohira?

Limited express trains between Okayama and Kotohira do not even pass through Sakaide! So yes, you should buy the ticket for the non-covered section from Utazu to Kotohira. Whether to use reserved vs. non-reserved seats is a different question that comes down to personal preference. Since Okayama is the first stop along the train ride, you have usually pretty good chances at getting an non-reserved seat, especially if you line up at the platform a little bit in advance.

Thanks Uji, I was unaware. I looked at the coverage map from JR West and it showed Utazu, Sakaide and Takamatsu. I do remember passing through Sakaide on my way to Kotohira from Takamatsu in November. I didn't check to see the actual route of the trains from Okayama. Thank you! I save 100yen by purchasing the ticket from Utazu instead of Sakaide.

I find the train section between Sakaide, Utazu and Tadotsu to be one of the most confusing and exciting in all of Japan with limited express trains (and other trains) entering and exiting in all different directions.

Have a good trip!