WARNING: This comment may have spoilers.
Kyou Kara Ore Wa!! is the story of two boys, Mitsuhashi and Itou. They have both decided to switch schools and that from that day onward, they would be delinquents.
In the first few volumes, we get an idea of the characters we will get to know in the manga. The first main character, Mitsuhashi, is a conceited guy who will use any means necessary to win. This includes using tricks, pranks, weapons, and even using other people. However, he's no pushover, he has incredible speed and is quite intelligent and uses these things to his advantage. Our second Main Character is Itou, a complete opposite of Mitsuhashi. He's a nice guy who only fights for justice, protecting the weak and to help others, however he is quite naive. In fights, Itou fights fairly and because of this he loses most of his fights due to the opponent using unfair means to win. Itou lacks speed, but makes up for it with brute strength, being able to take a beating but still keep going. Our side characters grow but there are only four important side characters to the whole story: Imai, Tanigawa, Riko and Nakano. Imai and Tanigawa are from beni high, Imai is like a gorilla in terms of strength and is quite tall, however he's an idiot. Tanigawa is the opposite, small and weak like a monkey but is intelligent. Riko is a girl Mitsuhashi meets and later befriends, she runs a dojo with her father and later begins to fall for Mitsuhashi. Nakano is best described in a few words: the strong silent type.
Now then, the plot is kinda everywhere in this manga, but it does have one. In the first few volumes, it comes off as episodic and gag filled, but eventually starts to have storylines and arcs of sorts. The manga mostly follows the format of doing a few episodic gag chapters, major story arc, flashback of sorts and then closure for the arc. Then the cycle repeats. Most of the story arcs are about rivals from other schools trying to give Mitsuhashi and Itou trouble, or one of the side characters being in trouble and needing help.
Character development does happen, the best example being Imai and Tanigawa. Imai in the beginning was nothing but an idiot who fought for the sake of fighting. However near the end he has a goal for what he wants to do in life and why he's fighting. Tanigawa was known as just a weakling who followed Imai and at one point admits that he was weak and nothing would change that. But due to certain events, Tanigawa mans up and eventually proves to everyone he is just as strong as even Itou or Mitsuhashi.
Overall, I felt Kyou Kara Ore Wa!! was great, it had everything you want in a comedy action manga about delinquents. It had gags, story and development and I would gladly recommend this to anyone.