Leona is the younger twin brother of Dorothy West and is of Canadian (his father) and Japanese (his mother) descent.
He is quite shy and would wither away if not for Dorothy. He often follows whatever Dorothy does as an example, such as pretending to faint if she would, or dislike someone if she does. This changes as the season continues and he starts to gain more confidence to do more on his own without Dorothy. He also becomes slightly more outgoing.
He has a relaxing atmosphere about him and can easily calm others, most notably young children. This is emphasized by his catchphrase "(Tension) relax!". Leona is also shown to be quite feminine.
(Source: Pripara Wiki)