Dr. Shamal

A crazed womanizer who hits on every cute woman he sees. Though often unsuccessful, he is always seen hitting on one woman and then instantly moves on to hit on the next woman that passes by him. Putting aside his normal attitude, Shamal happens to be a notorious assassin called "Trident Shamal", and is also a renowned doctor, who refuses to treat men. He uses trident mosquitoes to infect his targets with deadly illnesses. Since he naturally contracts viruses and diseases easily, he carries 666 pills that contain mosquitoes infected with deadly diseases.

He claims to be infected with 666 diseases, but is not dead because all his diseases negate each other (If he has a disease that rapidly decreases body temperature, then he has another one that increases it). Shamal also happens to be the one that introduced Hayato to bombs when he used to work for the Gokudera Family. Hayato initially wanted to learn how to use the trident mosquito, but Shamal taught him how handy it is to carry mid-ranged weapons. During the Vongola Tournament arc, he became Hayato's home tutor, but actually just watched him improve his skills while throwing paper airplanes as Hayato's targets. Source - Wikipedia