He may seem shy and bashful on the surface, but...
Taito is a very fragile, poor young boy, who is often incredibly shy and nervous and he is usually by himself. He carries the burden of constantly being in pain. Every little scratch and scuff he gets, the mark may fade away, but he eternally feels an imprint of discomfort to the affected area. If he lost an android limb, even if it were to be re-attached, he would forever feel a line of stabbing pain along the socket.
However, even if this pitiful boy will have fits of his own where he'll scream in agony for it being too much to handle on him at once, while the pain is being caused to him, regardless of what it may be, Taito will grow to have a carnal appetite for it and he less shrieks in pain, but more moans in pleasure and salacity. This may be a reason for many to avoid Taito... they are deeply disturbed by the fact that he enjoys pain.
Besides this disturbing detail, there is another part to Taito that most do not see... unless they provoke him or arrive in his sight at the most grim of times...
If Taito is provoked, threatened, or finding himself in a situation where he feels as though he's going to get hurt, he will stop at nothing to defend himself, even if it involves killing.
In the event that Taito is threatened in these ways, he will turn absolutely violent, and even the person with the hardest shell and thickest skin turns absolutely terrified at Taito's bizarre transition. During this time, in his mid sentence as he speaks, his voice lowers from his usual slightly-high pitch to a much lower, demonic one. Horrifyingly enough, this brutal part of Taito is the only side of him that smiles... but these are no pleasant facial expressions.
Once Taito is through with one of these unfortunate happenings, he returns to his normal state, with no memory of his previous actions or attitude.
During those times where Taito loses himself, he will grab hold of an ice pick that he always has tucked in between his pants and his boxers, so you should know that provoking Taito will result in an ice pick stuck somewhere in your flesh.
Back at the center where all the androids were made, before any of them were sent to CRYPTON to live, Taito was always the Shion sibling that hid in his room, away from the others, excluded from the love and the warmth. He was always the child that never came down to dinner, but came down to get the left-overs, if there ever were any. He was constantly the brother that always stayed home when the others went out.
Even if he's the one who pushes people away, it wasn't his fault. He was told by the scientist who created him that he was a purposeful failure, and from that scientist, he never received any affection. He was rejected from the one who built him, so he rejects himself from everyone else, thinking that that's the way things are supposed to be. Despite this, Taito is always unconsciously mentally holding out his arms for a hug and screaming at everyone for attention. He is always thinking in a hidden part of his brain, "doesn't anyone love me?".
Taito is rumored to have once stabbed himself in the left eye on purpose, or fallen over his clumsy feet and landed with some sort of sharp object to his eye.
No one really knows if Taito was purposefully made to have "episodes" of suddenly going off psychotic, or if something may have happened to him to permanently twist and taint some part of his mind...