Rin may seem like your next door bratty neighbor, but there's more than what meets the eye. He may be only 7 years old but he posses great ESP powers. Being able to fly, teleport, imatate someone else's voice, make things fly, create lots of destruction, and etc are what he specializes in. He's a very clever kid too (being able to send his own Love Letters and Death Threats :) Even before his 'accident' Rin seemed very adult (at least to Alice).
Most of the time Rin seemed like an evil little boy. He manipulates people who are a lot older than him (i.e: Haru, Takashi).He blackmailed Takashi while trying to get Tokyo Towers and later on, Haru for the keywords. He also broke Mr. Tamura's ribs!! He's definitely not your normal 7 year old!
In ep. 3 Rin reveals that he is the reincarnation of Shukaido. Saying he had died once before (killed by a car actually) and this was his 2nd reincarnation. It seems that Rin is also a good liar too... But in fact Rin is really Shion, not Shukaido! So why is he just a kid when everyone is 17? Because... because... nah I won't tell you. Just go to Shion's page to find out! ^_-
Despite all of that, Rin is just a kid. And there are times that he will act like a spoiled little brat. Sometimes, he will just break down and cry in Alice's arms. Poor kid... What Rin wants the most is to be with Alice. And since they are separated by 9 years, there are many complications between them...
It's hard to determine if Rin is really evil or good. His actions are questionable... still Rin can be a sweet kid when he wants to be :)