BL Metamorphosis

I'm surprised that no-one recommended these two series before. There're age gap friendships in both of them. and also we see that older person who discovers new passion and encourages the young one. They shares same hobby etc. You should try watching both

BL Metamorphosis is based on the bl manga world and its lovers whearas fujoshi..s 2ndoray character is a fujoshi

Also tackles an unexpected friendship between an old woman and a teen girl. If you're into this kind of story, make sure to try this one.

The atmosphere and storyline of both is pretty different, but what is similar is that we see two women bonding over, in one, their love for BL manga and in the other, their passion as fujoshis.
Both of them do not exactly consist of gay/BL romance but feature main characters who are fans of the BL genre.

It's such a surprise that no one recommend it, in BL Metamorphosis, they are reading I Just Want to See You manga and become close friends

I actually haven't started to watch My Grandpa is a BL Writer but from the description and title it reminded me BL Metamorphosis