"[Jupiter] has the best grades, and coaches make her starter on whatever team has the most pressing need for someone who can do sports. She's a perfect role model, except for how she always misses the winning goal and blanks on the last question. She leads when no one else wants to, which is always."

From the wiki: Jupiter typically has a "go with the flow" type of attitude, and doesn't concern herself much with other events. The only main exception to this is her fear of the Devil and of being a bad kid. She is constantly afraid of being "bad," and goes out of her way to try extremely hard to be seen as good. 

Jupiter should have a generally relaxed tone with most lines, but the voice actor should also be able to smoothly shift to and from a more nervous or upset tone over a few lines.