While I am not totally above having some fantasies of how it'd be to be dating a fictional character, imagining dating an
anime character is quite more difficult.
So, better to associate a real-life person with the character. For Sheryl... hm. I'd probably still take a young Christina Aguilera. Even if Beto goes once again apeshit at the thought.
Heh, I have few characters in Frontier I could actively associate a real life famous person with. No idea for Ranka. Alto maybe a young Takeshi Kaneshiro ( Samosuke Akechi from Onimusha 3 ), with his father played by Toshiro Mifune, Shogun ( TV miniseries ) era.
Captain Wilder I associate strongly with Liam Neeson, but outside of that I am drawing a blank. ^^
Anyway, that got a bit off-topic.