Hi! I think this is the one you're looking for!
https://www.mangago.zone/read-manga/mask_danshi_wa_koishitakunai_no_ni/
Description: "Mouth is the second sexy body part".
The famous cheerful guy, Saikawa had tried to rip off the gloomy kid, Sayama's mask.
After that day, he had captured Saikawa's attention and Saikawa had volunteered to teach him for the upcoming examination but with one condition, Saikawa can do whatever he wants with what is hiding under Sayama's mask.
i'm not speaking for the poster but i'm pretty sure the ml is insecure about his mole next to his lips and not their lip size in that one
Thank you, maybe it's this one?
https://www.mangaupdates.com/series/nfsohda/saikyou-yankee-ga-mask-danshi-ni-natta-wake
Lip complex is mentioned and I checked several sites and can't find it op unfortunately!
Thanks I've been looking for this in months （/TДT)/
The uke has big lips and is insecure abt them and hides his lips with a mask.
The seme and the uke was childhood friends where seme fell in love after like seeing ukes lips and kissed him.
Years later seme transferred to another school and met a yankee with a mask and later found out the yankee was the childhood friend.
I just need a name I dont think its translated yet idk but the name was like yankee or something