It's pretty simple really. The characters look, sound, and act like the characters in SZS. The animation, soundtrack, sound effects are all similar for obvious reasons. The quirky randomness is the same. The way the story seems to take place at school, but the characters meet around town and engage in silliness is the same.
But as stated earlier, it's a prototype. As you watch, you can tell Kette ni Kaizou is less mature and sophisticated than SZS. The former has less social commentary(though it does happen occasionally) and replaces it with ridiculousness, sexual jokes, and general being over the top.
Since these connections are so clear, they are constantly in your mind as you watch. I'm sure this was done intentionally to ride on SZS's popularity but that's what's holding it back. It doesn't have it's own identity, and will always be overshadowed by it's better and more successful older(or younger depending on how you look at it) brother. It's still fun, enjoyable, and funny, just not great.
