This article aims to consider how Internet addiction, particularly smartphone addiction, exerts a negative influence on the morality of Japanese youth. Particular attention is paid to the loss of "relationship", which is considered in this article to be the basic factor of morality. First, this article points out that "overestimating friendship and communication" is a fundamental factor of Internet and smartphone addiction. Furthermore, Internet and smartphone addiction is worsening the overestimation of friendship and communication. There is an interrelationship between overestimating friendship and communication and Internet and smartphone addiction. This interrelationship then results in the loss of the ability to have relationships with "others" and "oneself'. In section 1, this article discusses the loss of the ability to have a relationship with others. In this case, others includes all individuals existing within our society as well as culture, history, and nature. Overestimating friendship and communication and Internet and smartphone addiction lead to "the decay of public spirit". In addition, this article refers to several problems such as child prostitution and the spread of obscene information, which are becoming more prevalent because of easy access to dangerous persons and harmful information via cell phones and smartphones, considered the "perfect personal device". In section 2, this article discusses the loss of the ability to have a relationship with oneself. Here, the ability to have a relationship to oneself refers to one's own ability to have an effect on oneself, for example, self-reflection, self-discipline, and autonomy. Overestimating friendship and communication and Internet and smartphone addiction produce numerous problems in children and youth including little self-reflection, narcissism, and a decline in general ability.