Kaito is Kei's childhood friend and the only human person in the entire country who makes an effort to help Kei despite the fact he is an Ajin.
Kaito is shown to be a very loyal and supportive friend for reasons not yet made known. Without hesitation, he helps Kei flee despite the fact that Kei had rejected him as a friend.
Though situations become increasingly worse, he appears to retain a very positive, determined attitude. He is very resourceful and though he is not as intelligent as Kei, he is able to make tactical decisions while they were on the run together.
(Source: Ajin Wiki)