I'm putting my money on a collab as well.
The only idol-collab that would justify such a fuzz would be MomoClo but they got bigger fish to fry.
A K-pop collab? What a friggin' nightmare that would be!
My guess -
1. The silhouettes are obviously men.
2. Akutsu-san mentioned them as one of his favorite American rocks bands. The other bands mentioned (Guns, Ozzy, Aerosmith) are out of the question.
3. Passpo is his pet-project, he does whatever he likes, no matter if it makes any sense or not. I mean, who of you guys knew who Josh Freese is?
4. So it must be some 5-man rock band, most likely American 90's dudes once successful, trying to revive their popularity in Japan.
5. It's like following the latest idol x western (hard)rock band collab-trend. But as Passpo started this trend themselves, they got every right to jump that bandwagon.
-> it's Skid Row.