This WEBTOON really hits close to home because it's about a guy who surrounds himself in dark sludge since my guess is that it's to do with social anxiety in school and there he meets a potential friend Suni who seems she's a loner too. The personalities of each character and the detail of how the protagonist is feeling really is worth to get yourself lost to his own world. You can read this on the WEBTOON site with daily passes involved, it's pretty decent enough read and it’s really worth checking out if you like the psychological genre within your manhwa collection!