Not going to bother, these are backgrounds from Arcanum Stone.
I think the key is on the games and programs list page
素晴らしい絵やで…
すばらしいえやで…
subarashii e yade...
"These drawings are wonderful..."
And the comments are just explaining that he's not the one who made the pictures.
Dang, really good but those are just static images right?
Static background yes, and everyone is allowed to reuse the pics, permission granted by Hirai who made those.
But as good manners, don't just claim it's yours.