Note that, don't take this show very seriously, it's a joke that exaggeratedly a stereotypes. This show isn't trying to define a person's personality based on their blood type. Somehow the problem is just with their individual personalities (or so the narrator has been said). Well, it is common among anime and manga authors to mention their character's blood types, and to give their characters corresponding blood types to match their personalities, same goes with the video games.
Not much should make this show more entertaining rather than the comedy itself. Blood type A might have something Blood type B don't have, and vice versa. You also can see their different reactions from same kind of situations. But the personalities they presented ain't very accurate as well. Currently, there's no scientific research that proves blood type can be much affects the person's personality. But surprisingly from this show i find the accurately percentage might be 40-60 % since I knew and heard most people has the same weakness or advantage with characters here. I, myself included. Well, yeah my advice you can just take the lessons from here, don't do what they ludicrously do.
That aside, the characters design is kind of adorable to the excess that their face are showing their own blood type, it's so simple. Purposely for focusing to divides their personalities as well.
Even the music ED describes their personalities but it did well for trying to tell they should get along with each other. And for the cast voices this anime really has a great line-up of seiyuus. They're most known people for the popular characters they're voicing, and here the voice is what i could say accurate and most fitting for the characters.
Ultimately, what this anime only lack is the duration, seriously in only 2 minutes the conversations is being rushed like blablabla and blablabla tara! the ED song is playing. People have been mentioned this. You're gonna find it hard to get what they're saying unless you press the pause button for every long-and-fast talking they made. I even replay the episode for 2-3 times to really get or understand what the plot they're hinting. I know I am not the only one. I’m quite sure this has a slim chance of a third season.