This is classic example on 'Great actor - Not so great show'. Miura Haruma shines as Kotarou. He is able to play two sides of himself magnificently and shows true skill, but the rest doesn't follow up. Maybe had everyone had his acting skill, they would be able to lift this poor story that doesn't really contribute to anything. It's predictable and, well, really boring at times. The only thing that made me watch the whole thing was the transformations from school boy to samurai.
Ofc, it's not only bad. It has some funny moments and some (imo) good choreographed fight scenes (for being amateurs).

It's also a 'moral speech' drama, so you get a moral speech about the incidents from the episode in the end (kinda like Gokusen). And that's good, for those who like that stuff.
If you're looking for something to watch because you don't have anything else to watch, I say go for it. If you're looking for a hilarious drama or an exciting drama with plot twists or some deep meaning, I say go look elsewhere. Imo, it's just Miura Haruma that makes this worth watching, and even if it was Oguri Shun (fangirl, sorry) that just isn't enough. Too many things are missing to make this a 'good' drama.
Hope you found this helpful. :P.