Remember those pet carriers with a bubble viewing portal for carrying your pet around town? "How could I forget, I bought one." Same here, plus in different colors to coordinate with my outfits. Anyway, because competition is the mother of
innovation getting angry at a competitor and burning their factory to the ground, these are the pet walking backpacks available from Thanko (5,980 yen, ~$55). They're available in black or white and are suitable for one 8kg (~17.5-pound) cat (PROTIP: if that's not a Maine Coon it should probably be walking to burn some calories), a 6kg (~13-pound) dog, or a shit-ton of gerbils or hamsters. Don't have a real pet? Carry around a stuffed animal! People will think you're weird but that's okay because you are.
Keep going for a bunch more product shots and a short video showing a pet's-eye-view from inside the backpack.
Thanks to v, who agrees this is not the backpack for fish.