This from a Shonen Jump poster from 2000, so it narrows down where he's from to a series from it released 1999 or earlier
>>1557163Looks like One piece.The girl(?) of the right looks like Robin
>>1557170Not op, but Shonen Jump often creates art featuring an assortment of their characters
Not even Gelbooru knows, wow. Also the poster is from 2008, it's celebrating 2000 issues.https://gelbooru.com/index.php?page=post&s=view&id=919141
If you can find (good luck lol) WSJ 2008 #49, apparently Murata wrote some comments about the poster there, so maybe there's more information about the characters in that issue. The poster first appeared in WSJ 2008 #34 though.
Ah, I figured it out after some more googling.It's Anabebe from Jungle no Ouja Tar-chan, something I never even heard of.https://myanimelist.net/character/94515/Anabebe
>>1557195Thank you! I've never heard of this either