It's not really shounen ai but its yaoi and its like a tragedy and called saha and then there's another called December rain (It's a full color webtoon) and there's one where its a yaoi thought but its not like explicit so its more shounen ai ig http://www.mangago.me/read-manga/life_senjou_no_bokura/
TEARJERKER
list is a collection of
• happy ending
• bittersweet
• sad/tragic
http://www.mangago.me/home/mangalist/636848/
i recommend this for quick read
#021 http://www.mangago.me/read-manga/hate_no_kouya_de_vacances_wo/
#022 http://www.mangago.me/read-manga/hypnosis_mic_hoshi_ni_naru_made_doujinshi/
You can check the comments section if you want to know which mangas have happy/bittersweet/tragic ending
Follow the list to be updated. And if you liked the mangas/manhwas I included, please do recommend. Enjoy~ (人 •ᴗ•)
Manga that is shonen ai, something makes me cry