I also asked on the mangago subreddit but nothing idk if someone here will be able to help, I don’t have much info on it since I saw slides of it on TikTok. It’s a historical(?), comedy, enimes to lovers/I’m pretty sure this is what it is/ I remember the top having short blackish grayish hair and the bottom having long Brown hair he wore in that half up half down hairstyle… also I do t remember if it was an arranged marriage or something cuz they were in a relationship already… pls help I’ve been wanting to read so when I went and looked for it in my list I saw it wasn’t there ╥﹏╥
At first I thought it would be this one but it doesn't 100% match your description
https://www.mangago.me/read-manga/bad_friend/
Here are some lists it might be in based on your description
https://www.mangago.me/home/mangalist/1002089/ https://www.mangago.me/home/mangalist/625264/
Sorry I couldn't be of much help but I hope you find it!
Most of yall in the comments hurting my head not understanding his character… he’s not an airhead or dumb, imma take him under my neroudivergent wing lol