A siren can fall in love?

Siren are known to be violent. Their violent nature often warrants an immediate death sentence. Many people were killed

And yet Isagi was the sole researcher for the siren named Kaiser.

The first time they met Kaiser try to Isagi. And next time.. and next time. It became a routine at that point.

Kaiser try to kill Isagi as usual but that time Isagi fainted from exhaustion. Instead of killing him. Kaiser looked worried and pulled Isagi back to shore.

After that day Kaiser becomes less hostile. The murder attempt is still there, but sometimes Kaiser just doesn’t touch him at all. He allows Isagi to swim freely anywhere he wants.