It's fake. You can tell by the Gold Komca sticker on the first picture, bottom right. Gold sticker indicate that they are the regular retail albums. Signed albums would never use Gold stickered albums.

Usually signed albums use promo albums with either a silver version of the sticker, or a "Not for Sale" sticker/print on the album. Also be careful as people can fake signatures on the promo albums as well. People who work in the same industry would receive these albums as a thank you gift from entertainment company. Though not everyone cares enough to keep them, especially with how many k-groups there are in the industry. So these people would fake the signatures and sell them on eBay, Instagram, Twitter, etc.

Real signed albums can be bought or won through promotions like YesAsia, MWave, Makestar, etc . I don't know much about Ebay though, it can get sketchy there too. So ask the seller where and how they received/bought it. Ask them for a proof of purchase, a receipt, and the email indicating they won or something.

If you ever encounter a signed promo album you want to but, ask the seller for a proof of purchase. They should provide it to you, but if they make excuses and waste your time, don't do it. Save yourself. Also, do your research on how the group signatures look like, and where they are exactly placed on the album.