Danbooru has translations, but you're going to have to really search for them depending on your account (or lack of). Ao3 also has a good chunk of Reimari, and a whole bunch of other well written works for various ships. You can also go straight to the source and search around on pixiv, but likely that won't be a fruitful as the others.
Worked on classifying pretty much all the ReiMari doujins in danbooru. You just have to search Reimari in the description search in the pools page to get them now.
Highly recommend reading this one btw: https://danbooru.donmai.us/pools/15018
The grey summit might be pretty interesting with Sakuya, Youmu, Sagume, Eirin, Nazrin etc. Also Hijiri has both blonde and purple so wonder which summit she belongs to
