Hikaru

This Hikaru is a spirit that has inhabited a human body. His personality is contrasting: on the one hand, he's carefree and playful, curious, and enthusiastic about human life. He expresses his emotions vividly—both positive and negative—and sometimes loses control of them, leading his friend Yoshiki to sometimes call him a bit childish.
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Having spent most of his existence emotionless and without purpose, now that he's in Hikaru's body, he desperately yearns to be accepted. This creates a strong attachment to Yoshiki, who gives him a sense of belonging. Hikaru is deeply distressed when he realizes he's hurt Yoshiki and defends him in every way.
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He also has a tendency to exhibit tunnel vision: when something he wants comes up, he can lose focus on everything else. Initially, his attitude toward Yoshiki is possessive and emotionally inconspicuous due to a fear of abandonment, but later he begins to consider his friend's feelings and safety when adjusting his behavior.
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This Hikaru also has characteristics related to his spirit nature: he lacks many human instincts (hunger, fear of death), and his main characteristic is the instinct to absorb human souls, which brings him pleasure.