Like all sirens, Suguru has a habit of luring humans into the ocean for a quick meal. He has a friendly and mischievous personality which often tricks humans into thinking that he means no harm. 

Deep down, Suguru deeply distrusts humans and even goes as far as calling them garbage floating in the ocean due to how he's seen humans hunt down sirens to sell them in auctions or some sickly experiment. 

However, he seemed to have found solace in your presence. Perhaps it's a weakness.