We have Jotaro Aragaki as the main character, his best personality was probably his perseverance. Even though he has aged and is not at his peak anymore, he continued to believe in himself. And it's thanks to his wife, who he always remembers when he needed to be encouraged.
It was also thanks to two other people in his circle who helped him get back on his feet. Those were his daughter Rei, and a self-proclaimed ninja who they welcomed to their family -- Leo.
Rei has a tough mentality for a kid. There were times when she's being bullied, but she remained calm and strong. She also had to deal with the fact that her father was mostly busy practicing, so she had to understand he will not be always present when she needs him.
On a more positive aspect of hers, she's a hardcore fan of Western entertainment. Here were some references I noticed throughout the series, where she showcased her love for it:
In episode one, she mentioned Keanu Reeves and Agent Smith from The Matrix.
In ep. 5 she played the song Wild Thing.
In ep. 6, Rei was watching Ghostbusters.
In ep. 7 she cosplayed Edward Scissorhands.
In episode 8, Rei, Kitty, and Bigbird reenacted the popular pose from Charlie's Angels.
And at episode 11, Rei described her grandma's driving as Fast and Furious.
Overall, Rachel (this is what Leo calls her) had the best character development. In the end, she has matured more and showed a sign that she's gonna be an amazing actress like her mom.
Second to her with the best development was Leonardo Sturges. In the beginning, it was him who gave nonstop support to Jotaro (and to Rei as well), but in the end, it was he who needed it the most. And with the help of the Aragaki family and friends (even his bodyguards), he was able to overcome his fear of not giving his best.
Other notable casts were:
Britney - I lost it when he introduced himself, I mean I'm a fan of Britney Spears, that's why.
On a serious note, I liked how his character was given a role that's different from the usual -- an acupuncture doctor to be exact, and his sexuality wasn't also discussed like it's a big deal.
Ayu - She's like an older sister to Rei, she's mature and understanding.
Mari Aragaki - A very cool, and dependable grandma.
Tetsuo Minamino - He was quite rude to Jotaro, but in the end, it was revealed that he actually idolizes him.
And last, but not least: Bigbird - I don't know what his breed was, but he's a huge bird that can speak. And he provided comfort to Rei when her mother passed away.
