Glad you enjoyed playing it!
For me, it's hard to choose between them since I have to love them all. Aesthetically though, I like Aiden the best - solely on body type/looks/age.
To design the characters, some of the voice actors (who are my friends and have been since the start of the project) came up with how they would want their character to look. So, I elaborated and created them. The original start-of-project cast VAs were for Rei (Minami at the time), Aiden, and Jun. Rei's voice actor was originally supposed to be Minami, so he's where Minami's concept came from (aka cute, pink, cinnamon roll). Otherwise, Rei, Leo/Griffith, and the side characters were my own concepts, with the input of the rest of the team.