Here are some:
https://www.mangago.me/read-manga/purple_hyacinth/
[Hetero] (One of my personal favorites, captivating story and greatly paced romance between the two main characters)
https://www.mangago.me/read-manga/your_smile_is_a_trap/
[Hetero](A more light-hearted and cute one. Although this one has a lot of misunderstandings, they make a lot of sense once you delve into the story)
https://www.mangago.me/read-manga/the_lady_alchemist/
[Hetero](I was told this one was a slow burn but it's still at the first few chapters so take this recommendation with a grain of salt)
https://www.mangago.me/read-manga/igarashi_kun_to_nakahara_kun/
[BL](This one's really cute, I would consider it to be a slow burn because of the confession timing and the mc trying to figure out his feelings about the ml)
https://www.mangago.me/read-manga/for_your_love/
[BL](Another personal favorite of mine)
https://www.mangago.me/read-manga/ao_no_flag/
[Love Triangle](Won't say too much about this one because it is a must-read. It tackles some serious topics about love and sexuality in such a clear-cut way and how everyone is effected by those particular feelings)
Does anyone have recommendations for a relationship that is slow passed? thank you in advanced