Nature.
Curiosity (exploration), hostility (alertness), goodwill, appetite, loneliness, dependence (security), admiration, creativity, expression, vanity, sexual desire, laziness, selfishness, jealousy, possessiveness (control), destructiveness, fear, selflessness, protection (sense of mission).
This is natural.
This is the story of Taiya Ryo and Shindo Hikari.
There is no outline, the plot direction is unclear, and there are many clues, so proceed with caution.