Many voluntary activities for reading picture books with children have become popular in recent years. Since the “bookstart” activity started in Japan, there has been an increasing awareness of the significance of parents and children reading picture books together. We know that picture books are indispensable for good communication between parent and little child in the child’s pre-speech stage. The phenomenon of parents and children reading picture books together has several familiar characteristics : the effective enjoyment of the reading experience, admiring the pictures together, mimicking the text (mimesis), etc. Such co-reading involves authentic forms of sympathetic, harmonious, synchronic, etc. communication. Such fundamental communication generates children’s development of spontaneous speech acts. The aim of this research is to understand the nature of communication, i.e. communion, with particular focus on the the act of picture book reading.