Kanmangabuchi Abyss is not close to bus stops

Kanmangabuchi Abyss is not close to bus stops.   I visited there on November 7 with  young couple guests.  
They were fast walkers, so we could rush the way back from the entrances approximately  fifteen minutes to the bus stop, but  it usually takes more time.   It is a beautiful place and I know it's quite popular with International tourists.

If you would like to visit there, I would appreciate if you would let me know that you're interested in beforehand, or at the beginning of the day, instead of saying so just an hour and half before the train.

I once declined, because we were running out of time, and maybe the guest didn't understand it was far from the bus stops.
His wife had sprained her ankle some days ago, and said it still hurt, so I prefer to avoid making her extra half hour walk.