slippery slug's album - Sauce

[RESOLVED] Is there a sauce for this? Or is it just standalone art?

[FOUND] Who’s this fine gentleman?

Courtesy of this kind hooman: https://www.mangago.me/home/people/1817662/home/

[FOUND] Who’s the guy with blue-ish hair and a white hoodie?

Credits will be put in the comments because of the character limit ^^;

[FOUND] Where is he from?

Courtesy of this kind hooman: http://www.mangago.me/home/people/563713/home/