Black cat is an good manga, first we will speak of the positives aspect :

1.- The series beyond being a shounen, tells the story of a young man who was in a bad way and was not happy with his previous life, later he meets a girl who makes him reflect and change to be a free person , As well as valuing people.
2.- The characters are good and they are changing for the better in history, for example Train starts as a killer who works for chronos but who always dislikes that lifestyle, advances the time and becomes a good character with ideals of being Free, despite his life in the past.
Eve (my favorite character) starts as a girl without feelings and without knowledge of the outside world, over time matured her way of thinking and becomes more competitive, confident, strong and understands the feelings of her friends.
Sven did not change much but has an interesting story and is important for Eve's growth, between these 2 there is a father relationship and that I find it as a good detail for Eve's growth and in the final battle I helped to defeat several characters.
3.- The art is very good, especially the designs of the characters, have a style and identifiable another aspect that I liked were the battles was not only who destroys more, also develop a strategy to win the opponent and that for me It was entertaining.
4._ The comedy is good, but sometimes the characters may be in a moment of tension and go on to say a joke, but nothing that can be considered annoying.
Negative aspect
The villains, I know that many may like the villains, but I think it could improve the characterization and that these were deeper in personality, with motivations beyond "I will be a god and I will change the world" despite that I do not consider That that is something so bad in history, but they could improve that small aspect
 
In conclusion, it is an entertaining and fun manga, I know it is not better manga but I consider it a good story, I give a 9/10 to the manga as a critic, as a fan 10
Thanks for reading this review, I hope you like this story.