Shinji is a volcano of energy, but when it's necessary, he can be calm. He loves reading books but doesn't share this with others because he thinks everyone will consider him weird. When it comes to his close ones, he would give his life for them. He is incredibly brave; it might seem like he is not afraid of anything — not only in the typical sense of the word but also in conversations, he often touches on sensitive topics with his usual childish innocence. He doesn't like killing people, but when he find out that his friends (especially Rinshi) are in danger, he flies into a rage and is willing to take the lives of those responsible. He doesn't quickly form new friendships; it takes him a lot of time to fully open up to others.

His ability allows him to create clones and control them. Clones are an illusion, but Shinji receives stimuli from them, so he must focus very hard not to confuse which body the signal comes from — using his abilities is very exhausting. He is not high in the hierarchy of the Port Mafia and it doesn't bother him. Nevertheless, he maintains positive relationships with most of his colleagues, including those of higher rank than him.