Questions regarding Koyasan.

Hey everyone, I've almost finished my itinerary for my Japan trip. I have a minor problem during the last three days. I was planning on going to Koyasan on the 18th of of June(my flight back is on the 20th at Narita Airport). However, I'll already be seeing alot of temples before that so I don't know if there are any other attractions in Koyasan that I want to see. As for staying a night in the temple, I've done it many times because I'm from Thailand and its nothing new to me. My question is that if Koyasan is worth the day trip. If I don't go to Koyasan, my alternatives are:
1. Tsumago and Magome hike and head to Kawaguchiko
2. Hiroshima and Miyajima.
3. Take a long trip to Sendai.

Any help would be appreciated. Thanks!

If you are afraid that you will have seen too many temples, it might indeed be better to skip Koyasan.

As for staying a night in the temple, I've done it many times because I'm from Thailand and its nothing new to me.

Maybe the concept of staying at a temple is nothing new to you, but I am pretty sure that the food, rooms and ceremonies at Japanese temples is very different from those at temples in Thailand.

If I don't go to Koyasan, my alternatives are:
1. Tsumago and Magome hike and head to Kawaguchiko
2. Hiroshima and Miyajima.
3. Take a long trip to Sendai.

These are interesting choices. I recommend to select according to your personal interest.

If you think you will have seen too many temples before Koyasan, I will pick up
2 Hiroshima and Miyajima

i chose 2 as an alternative also. both are UNESCO World Heritage Sites that should not be missed when visiting Japan. a very must-see!

Koyasan is not just temples in fact I found the temples to be of secondary interest to walking through the cemetery with its thousands of headstones and magnificent forest. It is truly a beautiful place if you are in to photography. I recently visited both Koyasan and did the Magome Tsumago walk.( both in snow ) I would be inclined to do both and perhaps delete some temples elsewhere. I personally would rather see Koyasan than Nara and would put Nikko ahead of Nara for sheer beauty.
Hiroshima is just another city unless you have a strong wish to see the atomic bomb monument. Miyajima I felt was overrated.....just what I felt , not a statement of fact.
I have had five trips to Japan now and would put Koyasan on anyone's list of things to see.

If Kamakura is on your list, it's what you can omit.

IMO the temples in Koyasan are not very interesting. Visiting the graveyard is great though. I went there both at night and again in the morning. Both times it was beautiful.

Thank you guys so much for valuable opinions. I've decided to make Koyasan as my daytrip and cut one day off my Kyoto trip. That way I can also choose other alternatives for my last 3 days.