Sachiko and Masato's firstborn: an autistic little boy. Hikaru hated to be picked up and held as a baby and did not grow in step with children his age, leading Sachiko to seek a doctor for him. Hikaru dislikes loud noises such as crowds, Buddhist chanting, and babies crying. He likes trains and memorizes many of them, including ones no longer running. Like many autistic people, when something is changed in his routine without any warning, such as a show switching times or being canceled, it upsets him, though later in the series he and his parents know how to handle the situation better. Later in his childhood, he shows some unique talents including cooking and mixing colors. Sachiko gave him his name because as she says often: "My boy came with the morning light."

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