I picked this up on a whim while out shopping, without having seen any reviews, and I'm happy to say I had a good time with it. It's giving me exactly what I wanted from it - a heartwarming story about a middle aged guy reuniting with his students and slowly being brought to realise that he isn't the failure he thought himself. There's also plenty of swordplay (and honestly I do love an overpowered or otherwise highly skilled protagonist in my manga). 

This isn't likely to become anyone's new obsession, but if you just want a light feelgood story I recommend.