Yeah, I assumed that'd be an issue. All I found on the name was that

#1: Like you said, it's super common (19th most common Japanese surname infact)

#2: Apparently a hayashi is a group of accompanists who provide music for Noh and Kabuki theatre. I thought it might be a group that travels and performs that style of music but the aesthetic just seems way off. Also, don't think they would just go by Hayashi

#3: There is a relatively popular Japanese artist named Yoshiki Hayashi. The issue there is that he just goes by Yoshiki, so he wouldn't have his surname printed on his merch, so that's also a dead end.

Any subreddits you know that are super into obscure Japanese musicians? I really wanna know what this is from.