Akane
I'm looking for a guided tour of Koya-san as I don't want to worry about getting lost on the mountain. And, I think it would make for a better experience with a guide to explain all the history and culture.
Akane
Try these websites below. Hope you find something you like!
Tours by locals. https://www.toursbylocals.com/Koyasan-Tours
JTB. https://www.jtb.co.jp/shop/itdw/info/e/tour_info/y2011/other/koyasan_1day.asp
Triplelights. https://triplelights.com/japan/tour/mount-koya-koyasan-1-world-heritage-site-1136
KCCN. http://www.geocities.jp/koyasan_i_g_c/guide/guide.html
Japanican. http://www.japanican.com/en/tour/list/?typecd=TOU&typegrpcd=TPA&destcd=V29&GN_tours
Experience Japan. http://www.experiencejapan.com.au/koyasan-1-day-tour