We went a few days before a major festival and the town was quietly very busy getting ready for the big event, that and it was raining. Loved our stay at Ichijoin.
They were very accommodating to me and my wife(lactose and soy) it seems they will cater to any allergy if you just let them know in advance so they can be prepared. They are vegan and so the lactose was the least of the problem. ie: email. They have someone there who speaks perfect English and was able to translate, give local travel recommendations and ensured our stay was the best. Rained cats the whole time we stayed, they offered an extra umbrella and even to walk us to the bus when we were headed out. Can't say enough good things about our stay. Ultra clean, what I had imagined it to be. Complete immersion but with subtitles(translator). I'd like to revisit in the fall when the leaves start to turn.

Spending a night at the Ichijoin is an unforgettable experience. Of course it is expensive, but, for me, it was well worth it. I stayed there for a night with my husband during our honeymoon trip around China and Japan.
After we arrived we had dinner - all vegetarian, wonderfully prepared (see the pictures)! Then we went for a hot bath (separately, as usual in Japanese ryokan) and when we went back to the room, the futons were ready for us to sleep. Early in the morning, we attended a Buddhist ceremony -- really magical and powerful. When we went back to the room, a generous breakfast was waiting for us.
The staff are Buddhist monks, some of them speak English -- though we speak a little Japanese and were prepared to practice :) They are really nice and friendly.
Also, Ichijoin is extremely clean. The inner garden is very well groomed.
A note about Mount Koya: make sure to visit around if you stay there. It is a truly peaceful, magical place.

Genuinely authentic. In this temple stay you truly are a guest. However, part of the enjoyment is observing the customs and rules. Amazing how you will notice the disconnect from the wired-in world after only a few hours. I recommend rising early to attend the morning sutra chanting. While fairly strict hours are in force, there is the luxury of beer! The food is fabulous and served by attentive junior monks. It can be a bit difficult to book in the busy season (think cherry blossoms), but worth it.