Cosplaying in Korea

Hello! I'm traveling to Seoul soon and there's going to be a Collaboration Cafe I'm really looking forward to. I have two questions:

• How can I make reservations through Naver? I understood that reservation is mandatory to access the first four days
• How is cosplaying outside of conventions seen? Can I do that? The cafe will be giving some kind of item to people who come cosplaying and I think I read there won't be changing rooms there so I guess that I can only come already dressed. I'll have to take public transport. The cosplay is pretty basic and doesn't really show any skin. I'd expect to get some weird stares (especially from elders) but I get that. I'm mainly scared to come off as the rude foreigner since I heard Japan has some pretty strict rules about cosplaying and I wondered if that was the case for Korea too.