Kaoru Mizuno is a member of the Simon Famiglia. He previously attended Simon Middle School, but transferred to Namimori along with his Famiglia after an earthquake hit their area. They chose Namimori because it is relatively earthquake free and are invited to the Vongola Decimo's Inheritance Ceremony. He is the eldest of the 7 students who transferred to Namimori Middle School, grouped with Yamamoto to protect Tsuna by patrolling the sports facilities in Namimori Middle School.
Kaoru is one of the eldest members of the seven transfer students, and one of the few members that doesn't resemble a middle schooler. Because of this, he's often labeled as a "hooligan" due to his appearance. Kaoru's appearance is similar to the rest of the Simon; he is often seen wearing his school uniform and is very tall and fairly muscular with blonde hair. Kaoru also has red eyes, a trait shared amongst the other members of Simon.
Many people are afraid of him because of his appearance, which has been described to look like a "hooligan;" however, on the inside, he is actually a quiet and shy person. Yamamoto is the only one who is nice to him and the first person to call him friend, and this made him happy, as seen from his tears. However he seems to easily resort to violence if he feels threatened. Because of this according to Kouyou Aoba he is known as "The Hospitalizing Devil Kaoru."
Weapons and Abilities
Kaoru has been shown to be physically strong and fast, as demonstrated when he threw a baseball so swiftly it appeared to disappear. He was also able to attack Yamamoto before he could even react and easily cause life-threatening damage with his Earth Flame. Kaoru has also demonstrated that he is resilient enough to react even after being stabbed and slashed multiple times by Demon Spade.
- Simon Ring: Kaoru, like the rest of the Simon, possesses one of the seven Simon Rings when unsealed by the Vongola Sin. When activated, the Ring transforms into a powerful drill-shaped blade around his arm, which can easily pierce flesh and bone with little force required, while the rest of his arm is covered in armor.
- In the Reborn! Fandom, his number is 31.
- Even though he's around Yamamoto's age, being second year when he transferred to Namimori Middle, Yamamoto mistook him as an alumni and even the father of another student due to his hooligan-like appearance when they first met.
- He has a Regent hairstyle like Tetsuya Kusakabe, but smaller.
- His pride are his role and duties for the Simon Famiglia.
- Because he was taken away by the Vindice without a fight with Yamamoto, he is the only Simon Ring Holder and tenth-generation Simon Guardian whose Flame has not been revealed.