This review contains a few spoilers.
In my opinion this anime had lots of potential, though the poor writing really pissed me off. I was extremely anticipating the second season of Sword Gai: The Animation because at the time when I was fairly new to anime, I never noticed the many flaws of this show. This is my first review so bare with me...
The whole concept was very captivating. When I read the description I instantly knew I wanted to watch season one. I found Gai's past to be somewhat unique compared to other backstories of other protagonists (such as Ryouta Sakamoto from Btooom!). I
also liked the fact that it got adrenaline rushing through my veins as I watched. The writing seemed a bit abrupt for me at some parts, though. Gai attempts to commit suicide though he survives because he was healed...If you're going to make Gai jump off of a building and land face-first onto the pavement and have him survive, you should've just had him visibly considering it, then have some other way of him meeting Himiko.
Animation-wise, this anime isn't so horrible. None of the movements of the characters seemed unnatural to me as I watched this series. The fight scenes were well choreographed and enhancing. Whenever one of the fight scenes were on and I was eating, I'd always put the plate down at wait for it to finish.
Not too bad with the sound either. I found myself really enjoying the music. Especially the OP.
The character design was half-decent. Some characters were dull and some weren't. Shin Matoba was one of my favorite design-wise. He reminded me of Shiro from K.
Okay. This is where I start to thoroughly explain why I'm not too fond of this anime. The second season really bothered me due to the fact that all the characters from season one seem to be thrown away (as in die) and replaced by the season two characters. It also somewhat didn't feel like Gai was the protagonist anymore. Too much was going on and I would've preferred if they had kept the season one characters alive longer rather than killing them off and replacing them (especially Marcus). Starting deep character development on characters in the first season and make them die in the second season that just seems downright pointless to me. If they were just going to have that happen then I'd rather have the story have less characters so it can focus more on Gai.
I was really disappointed because I was looking forwards to Sword Gai: The Animation's second season being released. As disappointed as I was, you should still give this anime credit. If you're looking to pass the time with nothing else to do, watch this anime.