Pretty sure it was a oneshot in a volume. Bit hazy on details as read it many years ago
Seme and uke have been possibly dating for sometime both are adults if i remember right
Uke keeps a diary and has written his fantasy in it. I think he exchanges diary with the seme. Or seme reads his diary accidentally. And seme sees the fantasy he has.
One day uke comes home and a home invader attacks him and i think blind folds the uke and has his way with him. Uke finds out it is seme doing this to make uke happy.
I think they end up exchanging diaries with his fantasies for other types of play

I'm so sorry I don't know the title. I am writing here because I was fascinated by this story you wrote and I want to read it T_T

BL maniac - szukam maniaków BL! 🐅

Not sure if this what you are looking for. Nothing about a diary, but the rest is similar.
Souyuu Ganbou no Hanashi
And the sequel is
Koyu Ganbou no Hanashi

sorry for the belated reply
it wasn't that one. Thank you though