Boku to Senpai no Tekken Kousai

Himeko is the daughter of the Koigakubo family, one of Japan's leading conglomerates. People say she has "violence-seeking eyes" because of her tendency to fall in unconditional love with violent madmen. Her bodyguard, Shuuji Aoyama, is contracted by the family to take care of her. These two, who call each other "Senpai" and "Shu-chan", have a secret... perhaps their relationship is not what it seems.

(Source: Comic Gene, translated)