Please find on this page some hotels in Okazaki.
Mishima lodge, which is a guest house of National Institutes in Okazaki, will be also available.
Mishima Lodge
http://www.orion.ac.jp/lodge/okazaki_lodge_en/index.html
Okazaki New Grand Hotel
https://www.grand-okazaki.jp/newgrand/en/
Grand inn Higashi-Okazaki
https://www.grand-okazaki.jp/grand-inn/en/