his appearance, Jim is every bit as mature as Gene, maybe more so.
He's Gene's partner, and always refers to Gene as 'aniki' (I've heard
that word used for 'brother' and also just for someone who sees someone
else as a mentor--Anime Village translates it as the natural-sounding
'Gene,' instead of an imposed translation like 'mentor' or something).
He's really an excellent mechanic. I'm pretty sure he thinks adults
are crazy. He has an unnatural attraction to his car, I'm afraid;
he's named it Ehefrau, which is German for 'wife.' Other than that
(and seeing Melfina as a mother figure), he's pretty normal.