i feel like i'm going insane trying to remember it, i read it a long ass time ago.. MC goes to this sort of...military camp i think? it's an underground complex of sorts with different levels. love interest/seme is a crazy mad dog type with light hair, i think white or silver, and they meet via video call where LI's voice is distorted and only his hands are showing, and he and MC talk about rare books i think.
passion?
THAT SOUNDS LIKE “PASSION”
YES THANK YOU
it seems like the oldest a main character is in manga/hua is like... 32. give me some characters who are at least 40 or something, or visibly aged with eye bags and crow's feet :')
https://www.mangago.zone/read-manga/7_confessions/
Bot is in his early thirties but top is older
https://www.mangago.zone/read-manga/old_fashioned_cupcake/
https://www.mangago.zone/read-manga/old_fashioned_cupcake_beginning/
https://www.mangago.zone/read-manga/first_of_summers/
MC is 40 y/o
CTK is very good at drawing old men
https://www.mangago.zone/read-manga/midnight_rain_ctk/
Also their art in tumblr is amazing
OLDDDD https://www.mangago.zone/read-manga/don_t_call_me_daddy/
You should look up Nanao Bohra's mangas as she usually uses older gentlemen in her stories.