Not really hidden and not too sickly like terminally ill.. (well maybe 1?)
https://www.mangago.zone/read-manga/a_gloomy_delusion/
(Transmigration, bloody nose, sometimes coughing blood)
https://www.mangago.zone/read-manga/sweetie_sweetie_sweetie/
(isekai, Transmigration, weak frail body)
https://www.mangago.zone/read-manga/flowers_find_a_way_to_bloom/
(Regression, Transmigration, deadly Sickly body)
https://www.mangago.zone/read-manga/kill_the_lights/
(Transmigration, body is weak but will get better through proper eating, exercise etc)
https://www.mangago.zone/read-manga/grieving_you/
(Transmigration, body weaker than previous)
https://www.mangago.zone/read-manga/monochrome_rumor/
(Transmigration, body weaker than previous)
https://www.mangago.zone/read-manga/cozy_obsession/
(Omegaverse, weaker and estrus)
https://www.mangago.zone/read-manga/to_deny_the_route/
(Isekai, Very Frail and always gets sick.. Forgot if it was deadly lol maybe)
Happy Reading!
(๑•ㅂ•)و✧
Can I get a rec where the mc is sick and hiding it and the ml ends up finding them not doing well? (Preferably bl and preferably where the mc wasn’t originally sick but reincarnated into a sick body)