I believe him to be very much autistic coded. He doesn't understand normal social cues at all, often getting up in people's space, snatching things, shouting while talking and being blunt about his opinions. He has his own words (Jan-speak) he uses to describe how he feels or things he doesn't have words for, and uses a lot of body language to express his emotions when they're too much for words. He loves animals (having been raised by tigers) and collects mountains of plush animal toys, and loves being around nature. Also, he's very headstrong and impatient, and habitually rushes into things without waiting for the right moment, because he wants to get it done as fast as possible. His favourite food is pork katsu and he's very possessive over it. He hates when people are mean to others, though can be somewhat selfish himself, and he's very sensitive to Evil Vibes™(zowa-zowa in his words) and too much of it can make him upset and agitated.
Further detail from submitter: He's just a little guy. Also, one of the important storylines in the show was that the other characters needed to learn and adapt to the way Jan thinks and acts in order to understand him and work together, rather than force him to be more "normal" for their own comfort. Sorry to ramble, gekiranger makes me feel hapi-hapi