Responses
Maybe Frenemies? They didn't promised to marry each other though. It's more of a "Long live" promise or something like that
https://www.mangago.me/read-manga/bad_friend/
Red string quests–Season 2.
Any cute childhood friend bl?? Would prefer it if it's historical. Totally love it when one of them already love the other while they're still young and promise to marry them